============================================================

U.S. Robotics High Speed Modems

============================================================


+----------------------------------------------------------+
|                                                          |
|   HOW TO USE THIS MANUAL                                 |
|                                                          |
+----------------------------------------------------------+

This manual contains operating instructions for Courier V.32
terbo, Courier V.32 terbo Fax, and Courier HST Dual Standard
Fax modems.

These modems have many similar features except for the
signaling they use to connect with remote modems at high
speeds:  V.32/V.32 terbo or HST.  Courier HST Dual
Standard modems use either type of signaling, depending on
the type of remote modem.

In addition, the V.32 terbo can connect at rates of up to
21.6K bps, while HST Dual Standards in HST mode can connect
at rates of up to 16.8K bps.

If you've purchased a Courier V.32 terbo modem, disregard
the instructions in this manual concerning HST operations.
Below is a brief description of the manual's contents.
#    Chapter 1--Operating and compatibility features
#    Chapter 2--Installation and testing
#    Chapter 3--Data mode commands
#    Chapter 4--Fax mode and Call Selection
#    Chapter 5--Queries and Help commands to display current
     settings, operational summaries, and other data

The Appendixes in Part II cover the following subjects.

#    Background information on error control, throughput and
     flow control
#    Summaries and tables
#    Dial Security operations
#    Troubleshooting
#    Online synchronous and V.25 bis synchronous operations
#    Additional features such as HST Cellular and voice/data
     switch
#    Procedures for modem testing
#    Glossary
#    Warranty/Service/Certification information




A NOTE ON COMMUNICATIONS SOFTWARE
------------------------------------------------------------

If you're using a computer rather than a terminal, you need
communications software.  Many brands are available, all of
which are based on the modem's AT command set.
Some users prefer their communications software to take
control of the modem, and are more comfortable with a
program that makes the modem almost transparent.   Others
prefer a program that allows them to use the modem's AT
command set sometimes, and their software at other times,
depending on the task at hand.  Review at least Chapter 3 so
that you have a basic understanding of the modem's
requirements and operation.

























+--------------------------------------------+
|                                            |
|  U.S. Robotics, the U.S. Robotics logo and |
|  HST are registered trademarks of U.S.     |
|  Robotics, Inc.  Courier HST Dual Standard |
|  Fax, Courier V.32 terbo Fax, Total        |
|  Control, and Adaptive Speed Leveling      |
|  ASL) are trademarks of U.S. Robotics,     |
|  Inc.  Any trademarks, tradenames, service |
|  marks or service names owned or           |
|  registered by any other company and used  |
|  in this manual are the property of their  |
|  respective companies.                     |
|                                            |
+--------------------------------------------+
TABLE OF CONTENTS
------------------------------------------------------------
How to Use this Manual                                     1
Table of Contents                                          3
Limited Warranty                                           6
FCC Registration Numbers                                   7
DOC (Canada)                                               7
Connecting to the Telephone Company                        7
Radio and Television Interference                          7
For Canadian Modem Users                                   8

PART I.  INSTALLATION AND OPERATION

Chapter 1--Features and Compatibility
Introduction                                              10
Compatibility                                             14
Fax Standards                                             15

Chapter 2--Set-Up and Testing
Package Components                                        16
Operational Requirements                                  16
RS-232 Requirements                                       17
Switches                                                  17
Front Panel Indicators                                    18
Installing the Modem                                      18
Testing the Installation                                  20

Chapter 3--Data Mode Command Summary
Command Set Usage                                         23
Basic Commands                                            24
Dialing/Answering                                         24
   Dialing (D)                                            24
   Dial Options                                           24
   Store Phone Numbers                                    27
   Redialing                                              27
   Answer mode                                            28
   Hanging Up (H, +++)                                    30
Setting/Using Defaults (&Fn, &W, Z)                       31
Configuration                                             33
   Echo/Speaker (En, Fn, Mn)                              33
   Result Codes (Qn, Vn, Xn, &An)                         34
   Modulation (Bn)                                        38
   Error Control/Data Compression (&M, &K)                39
   Data Rates (&Bn, &Nn)                                  40
   RS-232 Operations  (&Cn, &Dn, &Sn)                     42
   Flow Control (&Hn, &In, &Rn)                           43
S-Registers                                               43
Inquiry and Help                                          48
Testing                                                   48
International Calls (&Gn, &Pn)                            48
Miscellaneous Commands                                    49



Chapter 4--Fax Operations and Call Selection
Fax Operations                                            51
Call Selection                                            53

Chapter 5--Queries and Help Screens
User Inquiries (In)                                       54
S-Register Query (Sr?)                                    58
Phone Number Query (&Zn?)                                 58
Last-Dialed Number Inquiry (DL?)                          58
Stored Command String Query (&ZC?)                        58
Help Screens                                              58
   Stop/Restart Display                                   58
   Cancel Display                                         59
   Basic Command Set ($)                                  59
   Extended Command Set (&$)                              59
   Dailing (D$)                                           59
   S-Register Functions (S$)                              59
   Percent Commands (%$)                                  59


PART II. REFERENCE

Appendix A--Link Negotiation (Handshaking)
     and Error Control
Link Negotiation (Handshaking)                            60
   HST Mode                                               60
   V.32 terbo Mode                                        62
   Dual Standard Handshaking                              64
Error Control and Throughput                              64
V.42 Handshaking                                          64
MNP Handshaking                                           65
Data Compression                                          65
Flow Control                                              66
Throughput Guidelines                                     66
   Achievable Throughput                                  68

Appendix B--Summaries and Tables
The RS-232 Interface                                      71
Front Panel Indicators                                    73
DIP Switch Summary                                        75
Default Settings                                          78
Factory Templates
   &F1 Hardware Flow Control (Default)                    79
   &F2 Software Flow Control                              80
   &F3 HST Cellular                                       81
   &F0 No Flow Control                                    82
S-Register Summary                                        84


Appendix C--Dial Security/Remote Access
Dial Security                                             96
Remote Access                                            102

Appendix D--Troubleshooting                              109

Appendix E--Synchronous and Leased Line Operations
Synchronous                                              115
    V.25 bis                                             117
    Online synchronous                                   120
Dedicated and Leased Line Operations                     124

Appendix F--Additional Operations
HST Cellular                                             129
Voice/Data                                               130
Hewlett Packard 3000 Installations                       134
MI/MIC Operations                                        135

Appendix G--Modem Testing
Testing with &T                                          138
Ending a Test--&T0, S18                                  138
Analog Loopback--&T1, &T8                                139
&T2                                                      141
Digital Loopback--&T3                                    141
&T4, &T5                                                 142
Remote Digital Loopback--&T6, &T7                        142
Testing with Register S16                                144
Analog Loopback--S16=1D                                  145
Dial Test--S16=2                                         145
Test Pattern--S16=4                                      145
Remote Digital Loopback--S16=8                           146

Appendix H--Glossary                                     148

Appendix I--Technical Specifications                     161


























LIMITED WARRANTY
--------------------------------------------

U.S. Robotics, Inc., warrants to the original consumer or
other end user purchaser that this product is free from
defects in materials or workmanship for a period of two 
years from the date of purchase.  During the warranty 
period, and upon proof of purchase, the product will be 
repaired or replaced (with the same or similar model) at our 
option, without charge for either parts or labor.  This 
warranty shall not apply if the product is modified, 
tampered with, misused, or subjected to
abnormal working conditions.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@  REPAIR OR REPLACEMENT AS PROVIDED UNDER   @
@  THIS WARRANTY IS THE EXCLUSIVE REMEDY OF  @
@  THE PURCHASER.  THIS WARRANTY IS IN LIEU  @
@  OF ALL OTHER WARRANTIES, EXPRESS OR       @
@  IMPLIED, INCLUDING ANY IMPLIED WARRANTY   @
@  OF MERCHANTABILITY OR FITNESS FOR A       @
@  PARTICULAR USE OR PURPOSE, AND U.S.       @
@  ROBOTICS SHALL IN NO EVENT BE LIABLE TO   @
@  PURCHASER FOR INDIRECT OR CONSEQUENTIAL   @
@  DAMAGES OF ANY KIND OR CHARACTER.         @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Some states do not allow the exclusion or limitation of
incidental or consequential damages or allow limitations on
how long an implied warranty lasts, so the above limitations
or exclusion may not apply to you.  This warranty gives you
specific legal rights.  You may also have other rights which
vary from state to state.

To obtain service under this warranty, contact the U.S.
Robotics Technical Support Department by fax, (708) 982-
5235, by phone, (800) 982-5151, or by mail, 8100 North
McCormick Blvd., Skokie, Illinois, 60076-2999.  You will be
given a Return Materials Authorization (RMA) number to help
us keep track of your warranty request.  Once you have
received your RMA number, take or mail the product, postage
prepaid, to U.S. Robotics at the above address.  Include
proof of the date of purchase.  IMPORTANT:  If you ship your
unit, pack it securely, be sure your RMA number is visible
on the outside of the package, and ship it charges prepaid
and insured.  Modems without an RMA will not be accepted.

Should you encounter problems in operating this device,
follow the instructions in Appendix D in Part II of this
manual.  The appendix contains solutions to operating
problems as well as procedures to follow if there is an
apparent modem malfunction.


------------------------------------------------------------
FCC REGISTRATION
------------------------------------------------------------
     FCC68:  CJEUSA-73130-FA-E
     RINGER EQUIVALENCE:  0.4B
     FCC15:  CJE-0151-234

------------------------------------------------------------
DOC (CANADA)
------------------------------------------------------------

This digital apparatus does not exceed the Class B limits
for radio noise emissions from digital apparatus set out in
the radio interference regulations of the Canadian
Department of Communications.

Le present appareil numerique n'emet pas de bruits radio-
electriques depassant les limites applicables aux appareils
numeriques de la classe B prescrites dans le Reglement sur
le brouillage radioelectrique edicte par le ministere des
Communications du Canada.

CONNECTING TO THE TELEPHONE COMPANY
------------------------------------------------------------

It is not necessary to notify the telephone company before
installing the modem.  However, the telephone company may
request the telephone number(s) to which the Courier is
connected and the FCC information printed above.

If the telephone company has any questions or raises
problems, ask them to call the Technical Support Department,
U.S. Robotics, Inc., (800) 982-5151.

If the modem is malfunctioning, it may affect the telephone
lines.  In this case, disconnect the modem until the source
of the difficulty is traced.  Do not use the modem on party
or coin telephone lines.

RADIO AND TELEVISION INTERFERENCE
------------------------------------------------------------

This equipment generates and uses radio frequency energy and
if not installed and used properly, in strict accordance
with the  manufacturer's instructions, may cause
interference to radio and  television reception.  Courier
high speed modems have been tested and found to comply with
the limits for a Class B computing device in accordance with
the specifications in Part 15 of FCC rules, which are
designed to provide reasonable protection against such
interference in a residential installation.

However, there is no guarantee that interference will not
occur in a particular installation.  If this device does
cause interference to radio or television reception, which
you can determine by monitoring reception when the modem is
on and off, try to correct the problem with one or more of
the following measures.
#    Reorient the receiving antenna.
#    Relocate the computer with respect to the receiver.
#    Relocate the computer and/or the receiver so that they
     are on separate branch circuits.

If necessary, consult your dealer or an experienced
radio/television technician for additional suggestions.  You
may find the following booklet, prepared by the Federal
Communications Commission, helpful:

     How to Identify and Resolve Radio-TV
        Interference Problems
     Stock No. 004-000-0345-4
     U.S. Government Printing Office
     Washington, DC 20402

In accordance with Part 15 of the FCC rules, any
modification to or tampering with this device that causes
harmful interference to others may be reason for prohibiting
future operation.

FOR CANADIAN MODEM USERS
------------------------------------------------------------

The Canadian Department of Communications (DOC) label
identifies certified equipment.  This certification means
that the equipment meets certain telecommunications network
protective, operational, and safety requirements.  The
department does not guarantee the equipment will operate to
a user's satisfaction.

Before installing this equipment, make sure you are
permitted to connect it to the facilities of the local
telecommunications company.  You must also install the
equipment using an acceptable method of connection.  In some
cases, you may also extend the company's inside wiring for
single line individual service by means of a certified
connector assembly (telephone extension cord).  You should
be aware, however, that compliance with the above conditions
may not prevent degradation of service in some situations.

Repairs to certified equipment should be made by an
authorized Canadian maintenance facility designated by the
supplier.  Any repairs or alterations made by a user to
this equipment, or equipment malfunctions, may give the
telecommunications company cause to request the user to
disconnect the equipment.

For your own protection, make sure that the electrical
ground connections of the power utility, telephone lines,
and internal metallic water pipe system, if present,
are connected together.  This precaution may be particularly
important in rural areas.

CAUTION:  Do not attempt to make such connections yourself;
contact the appropriate electric inspection authority or
electrician.
     Courier High Speed Modems Load Number:  5

The Load Number (LN) assigned to each terminal device
denotes the percentage of the total load to be connected to
the telephone loop used by the device, without overloading.
The  termination on a loop may consist of any combination of
devices, subject only to the requirement that the total of
the Load Numbers of all the devices not exceed 100.




+----------------------------------------------------------+
|                                                          |
|   CHAPTER 1.  FEATURES AND COMPATIBILITY                 |
|                                                          |
+----------------------------------------------------------+


INTRODUCTION
------------------------------------------------------------

Congratulations.  The Courier modem you've purchased
represents powerful, advanced electronic design that offers
exceptional reliability, compatibility and flexibility at
all standard rates up to 19,200 bps or 19.2K bits per second
(bps).  The transmission rate between the computer and
modem, depending on your equipment and software support, can
be as high as 115.2K bps.

The following features and capabilities assure you of
superior reliability and performance.

CONNECTIONS UP TO 21.6K BPS
With our new implementation of V.32 terbo, two Courier
modems with this feature can connect at rates up to 21.6K
bps and fallback to rates of 19.2K bps and 16.8K bps.  These
rates represent a rate of up to over 30% greater than the
rates of standard ITU-T (formerly CCITT) V.32 bis modems
which are limited to calls of 14.4K bps or less.

QUICK TRAIN
Courier high speed modems can handshake and start
transmitting in less than 2 seconds, in contrast to typical
training times that range between 9 and 18 seconds.

HIGH SPEED CALLS--ADAPTIVE SPEED LEVELING (ASL)
Like most high speed modems, Courier modems fall back to the
next lower speed, for example, 19.2K, then 16.8K, if poor
line conditions warrant.  In addition, Courier modems detect
improved line conditions and shift upward again to the next
higher speed.

ASL keeps the modems online, always operating at the highest
possible speed, and constantly ensuring data integrity.

FAX CAPABILITY--COURIER FAX MODEMS
You can use your modem in Class 1, Class 2.0, and Group III
facsimile mode for sending or receiving faxes.

ERROR CONTROL--V.42/MNP
Data integrity is ensured when the modems connect with
remote modems that use the V.42 (LAPM), USR-HST, or MNP
error control protocols.  Error control is available on
calls at 1200 bps and above.

DATA COMPRESSION--V.42 BIS/MNP5
Data compression enables potential throughput of well over
60K bps on 19.2K or 21.6K  bps connections.  Couriers
connecting under V.42 or HST error control use V.42 bis
compression.

Couriers connecting under MNP error control use MNP Level 5
compression.  Achievable throughput of text and other types
of files is listed in Appendix A.

FLOW CONTROL/VARIABLE INTERFACE RATES
Flow control, required under error control, also allows the
local computer interface rate to be set higher than the link
rate, enabling greater efficiency and throughput.  If your
equipment and software support high rates, data can be sent
from the computer to the modem at 115.2K, 57.6K, 38.4K or
19.2K bps, regardless of the link rate.

VOICE/DATA SWITCH
A switch on the modem's front panel allows you to change
from voice to data and back again, without issuing a
command.

STORED COMMAND STRING
If you don't ordinarily use voice and data in the same call,
you can assign the voice/data switch a different function
that normally requires a command, such as resetting the
modem or executing a stored command string.  See Voice/Data
in Appendix F for instructions on use of the voice/data
switch.

ASYNCHRONOUS/SYNCHRONOUS CAPABILITY
Courier high speed modems operate synchronously as well as
asynchronously.  A personal computer equipped with a
synchronous interface adapter can call computers that use
standard synchronous protocols.  See Appendix E for more
information.

SYNCHRONOUS OPERATIONS WITH V.25 BIS
Used with computers that have a synchronous card and port,
Courier high speed modems combine the power of older modems
and automatic calling units in the mainframe environment.
They make synchronous connections by utilizing V.25 bis,
character-oriented (similar to BISYNC) and HDLC protocols.
See Appendix E for more information.

DIAL SECURITY
With Dial Security, you will be able to prevent unauthorized
access to a system with the use of Autopass, Prompting, and
Dialback.  See Appendix C for more information.

PROGRAMMABLE NONVOLATILE MEMORY
You can tailor your own default settings and store them in
non-volatile random access memory (NVRAM).  Each time the
Courier is powered on or reset, it operates at the settings
you've specified.

LINK RATE NEGOTIATION
The Courier automatically lowers its link rate to match a
lower rate of a remote modem, in both Originate and Answer
Modes, allowing connections with a wide range of installed
modems.

LINK DIAGNOSTICS
After each call, you can display a Link Diagnostics screen
containing information about the last call, including the
number of data characters transferred, line statistics, the
call's rate and the reason the call was disconnected.

MODEM DIAGNOSTICS
ITU-T V.54 loopback testing with the &T command options, and
earlier Courier Register S16 test options are available.
The modem performs three loopback tests:  analog, digital,
and remote digital.  See Appendix G for information.

INACTIVITY TIMER
You can set the modem to automatically hang up after a
specified number of minutes if there is no activity on the
phone line.

CALL DURATION REPORTING
The modem records the duration of your calls in hours,
minutes, and seconds.  This feature enables you to display
and print an audit of your calling activities.  You can
optionally use the modem clock as a real-time clock.

CALL PROGRESS DETECTION
An optional set of result codes (screen messages) lets you
know when a line is busy, a person rather than a modem has
answered the phone, there is no dial tone, or the distant
phone is ringing.

MODEM SETTINGS DISPLAYS
On command, the modem displays its current settings, a handy
way to check your transmission rate, S-Registers and other
operational controls.  The modem also displays the defaults
stored in nonvolatile memory as well as its default
configuration templates.

HELP SCREENS
The modem displays screens that summarize the command sets,
Dial command options, and S-register functions.

BOTTOM PANEL REFERENCE
Command summaries and other information are printed on the
bottom of the modem case.  A Dual In-Line Package (DIP)
switch guide makes it easy to tailor the switch settings to
your terminal or software requirements.

DIALING THE LAST-DIALED NUMBER
The modem has a buffer that stores each dialed number until
it is cleared by another Dial command.  A few keystrokes
cause the modem to redial the number in the buffer without
your having to enter the number again.

AUTOMATED REDIALING
You can put the modem into Repeat Mode to continuously
redial if a previous dial attempt fails to connect.  This is
especially useful in dialing services whose lines are often
busy.

QUOTE MODE
Set the modem to Quote Mode if you want it to dial an
alphabetic acronym instead of a numeric number.

















COMPATIBILITY
----------------------------------------------

The Courier adheres to the following standards, ensuring
compatibility with a wide base of installed modems.  Unless
other-wise indicated, V.32 terbo and Dual Standard modems
both conform to the listed standards.

NOTE:  The International Telecommunication Union (ITU-T) was
formerly the International Telegraph and Telephone
Consultative Committee (CCITT).

USR-V.32 terbo 21.6K/19.2K/16.8K/14.4K/12K/9600/7200/
               4800 bps (Dual Standard and V.32 terbo
               modems)
USR-HST        16.8K/14.4K/12K/9600/7200/4800 bps (Dual
               Standard modems in HST mode)
USR-HST Cellular
               Cellular connections at 12K/9600/7200/4800/
               2400/1200/300 bps  (Dual Standard modems in
               HST mode)
ITU-T V.32 bis 14.4K/12K/9600/7200/4800 bps
ITU-T V.32     9600/4800 bps
ITU-T V.22 bis 2400 bps
Bell 212A      1200 bps (also V.22)
ITU-T V.23     1200 bps with 75 bps back channel (optional,
               some United Kingdom and European phone
               systems)
ITU-T V.25     Answer sequence for calls originating outside
               the U.S. and Canada
ITU-T V.25 bis For synchronous communications using HDLC and
               character-oriented protocols
Bell 103       300 bps (ITU-T V.21 optional)
ITU-T V.42     LAPM error control, 1200 bps and higher
ITU-T V.42 bis Data compression, 1200 bps and higher MNP
               Levels 2, 3 and 4 error control, level 5 data
               compression, 1200 bps and higher
ITU-T V.54     Analog, digital and remote digital loopback
               testing















FAX STANDARDS
-------------
The Courier modem provides Group III-compatibility when
combined with Class 1 or Class 2.0 fax software.  In
addition, the modem adheres to the following standards.

TIA/EIA-578    Service Class 1 Asynchronous Facsimile DCE
               Control Standard
TIA/EIA-592    Service Class 2.0 Asynchronous Facsimile DCE
               Control Standard
ITU-T V.17     14.4K/12K bps
ITU-T V.29     9600/7200 bps
ITU-T V.27 ter 4800/2400 bps
ITU-T V.21     300 bps

Other compatibility features include the following standards
and certification:

#    Can be used with any computer or terminal that is
     compatible with the RS-232 standard interface.
#    Can be used with any computer or terminal that uses
     ASCII, the standard character code supported by most
     equipment manufacturers.
#    Is fully FCC- and DOC-certified for the uses described
     in this manual.





























+----------------------------------------------------------+
|                                                          |
|   CHAPTER 2.  SET-UP AND TESTING                         |
|                                                          |
+----------------------------------------------------------+


PACKAGE COMPONENTS
------------------------------------------------------------

Your Courier modem package contains the following items:
#    The modem you purchased:  Courier HST Dual Standard, or
     Courier V.32 terbo.
#    A STOP guide with listings of Courier DIP switch and   
     other settings recommended for a number of popular     
     communications software products, plus tips for a quick
     startup.
#    An RJ-11-C phone cord.
#    A power adapter.
#    WinFax LITE fax software and manual.
#    A Quick-Reference card
#    Your warranty card, to be filled out and returned to   
     U.S. Robotics, Inc.

OPERATIONAL REQUIREMENTS
------------------------------------------------------------

The Courier modem has minimal operational requirements.  Be
sure to read the information in the front of this manual
about radio and television interference and connecting to
the phone company.  In addition, you should be aware of the
following conditions.
#    Follow the operating instructions in Appendix E,       
     Synchronous and Leased Line Operations, if your phone  
     line is user-installed or if it is leased from the     
     telephone company.  Also referred to as private, these
     lines are used for a direct, continuous connection     
     between two modems.  The connection is made without    
     dialing.

#    If your modem is installed in a Hewlett Packard system
     that uses the Ack/Enq communications protocol, be sure
     to follow the instructions in Appendix F.

#    If the modem is attached to a computer instead of a    
     terminal, you need communications software.  The       
     software uses the modem's AT command set to control    
     many communications functions, including configuring   
     the modem, dialing, and answering calls, and also      
     enables the transfer of files and other operations.

     Some users prefer their communications software to take
     control of the modem, and are more comfortable with a  
     program that makes the modem almost transparent.       
     Others prefer a program that allows them to use the    
     modem's AT command set sometimes, and their software at
     other times, depending on the task at hand.  Whichever
     you prefer, review Chapter 3 so that you have a basic  
     understanding of the modem's requirements and          
     operation.

RS-232 REQUIREMENTS
------------------------------------------------------------

You'll need an RS-232 cable to connect the modem to your
computer or terminal.  Use a shielded cable to ensure
minimal interference with radio and television reception.

The modem takes a DB-25P (25-pin plug, or male) connector at
one end of the cable.  Computer equipment varies, however.
Check the serial port at the rear of your machine, which may
be labeled serial, comm port, or some other term (e.g., RS-
232).  If there are no labels, review your machine
documentation to find out which is the serial port.  (There
may be more than one.)  Don't use a port marked parallel,
printer or aux.

The physical serial port on the computer or terminal will be
either a socket (female) or plug (male) that typically
accommodates 25 or 9 pins.  For example, the port on the IBM
PC, PC/XT and most compatibles requires a DB-25S (socket)
connector, while the port on the IBM PC/AT and some
compatibles requires a DB-9S connector.  Apple computers
require a DB-25P, DB-9P or, more typically, an 8-pin round
plug connector.  Check your computer documentation or with
your computer dealer.

NOTE:  Appendix B includes a listing of RS-232 pin
assignments required to operate the modem.  Be sure to check
the appendix if you're not sure what type of cable you need,
or if you're building your own.  If your machine has other
than a 25- or 9-pin port, check your computer documentation
or consult your dealer to find out what type of RS-232
connector is required.

WARNING:  If you're planning to use the high speed computer-
to-modem rates of 115.K, 57.6K or 38.4K bps, follow the
instructions concerning the RS-232 cable in Appendix B.  The
guidelines there will help you to avoid signal degradation
at very high speeds.

SWITCHES
--------

Voice/Data
This pushbutton switch is used primarily to switch between
voice and data communications during a call.  Detailed
instructions are in the Voice/Data Calls section in Appendix
F.  The switch has multiple functions, however.  Options are
as follows:

#    Disable the switch
#    Force the modem off hook in Originate mode
#    Force the modem off hook in Answer mode
#    Have the modem redial the last dialed number
#    Have the modem dial the first number you've stored in  
     nonvolatile memory
#    Toggle Auto Answer on and off
#    Reset the modem to its defaults
#    Initiate Remote Digital Loopback testing
#    Busy out the phone line
#    Execute stored command string (default)

Volume Control
This is a slide switch underneath the right side panel of
the modem, near the front corner.  Sliding it toward the
front of the modem increases the volume of the modem's
speaker; sliding it toward the rear of the modem decreases
the volume.

FRONT PANEL INDICATORS
----------------------
Below is a list of the modem's twelve status lights, or
LEDs.  See Appendix B for descriptions of their operations.
     HS   High Speed     
     AA   Auto Answer    
     CD   Carrier Detect 
     OH   Off Hook  
     RD   Received Data  
     SD   Send Data 
     TR   Data Terminal Ready
     MR   Modem Ready (Power)
     RS   Request to Send
     CS   Clear to Send
     SYN  Synchronous
     ARQ/
     FAX  Automatic Repeat Request (Error Control)/ Fax mode

INSTALLING THE MODEM
------------------------------------------------------------

1.   Turn off the computer or terminal and its peripheral   
     devices.

2.   Examine the label on the bottom of the modem.  In      
     addition to the summaries and other information, the   
     label contains icons to aid in modem assembly.  Check  
     the interfaces at the back of the modem.

3.   Now review the attached interfaces.

4.   Check to make sure that the power switch is OFF; press
     it towards the zero in the 0/1 icon on the bottom
     label.  Plug the power supply adapter's small connector
     into the power jack at the back of the modem.  Plug the
     adapter into a standard 115-volt AC wall socket.

     Disconnect your present phone cable from the wall jack.
     Plug one end of the phone cable that came with the     
     modem into the modem's phone jack that is near the     
     wall-jack icon on the bottom label.  Plug the other end
     into the wall jack.

     NOTE:  Older telephone installations may not have the  
     appropriate modular wall jack and plug.  Adapters and  
     RJ-11-C connectors are available from your telephone   
     company or computer dealer.

     If you want to keep your telephone connected for       
     conventional calls, plug its cord into the jack at the
     rear of the modem near the phone icon.  You can also   
     use both your telephone and modem in one call, although
     not at the same time.  Voice/Data, in Appendix F,      
     explains how to switch control of the phone line       
     between the phone and the modem.

5.   Next, check the positions of the bank of Dual In-Line
     Package (DIP) Switches located in the well at the
     bottom of the modem.  These switches are set at the
     factory to the positions most users require.

     The STOP guide that came with the manual shows
     recommended switch settings for many widely-used commu-
     nications software products.  If your communications
     software is not listed, check your software
     documentation for its requirements, particularly for
     DIP switches 1, 4, 5 and 6.  You'll also find
     descriptions of switch functions and options in
     Appendix B.

     If you already know your requirements, use the guide on
     the bottom of the modem or the summary in the Quick
     Reference Card to verify the switch positions.

     NOTE:  If you have built your own RS-232 cable and it
     does not support Data Terminal Ready (DTR), set DIP
     switch 1 ON, for the DTR override.  The override causes
     the modem to operate as if the DTR signal is always ON,
     and enables the modem to accept commands.  Most
     purchased communications software, however, requires
     DTR.

     DIP switch 10 is explained under Setting/Using Defaults
     in Chapter 3.  Most users will want to leave this
     switch OFF, write their own defaults to nonvolatile

     memory (NVRAM), and have those defaults loaded at power
     on.

     The wider Quad switch on the right of the numbered
     switches should be left OFF unless you know your
     equipment reverses the transmit and receive pins at the
     RS-232 interface (see Appendix B, DIP Switch Summary).

6.   The final step is to connect the modem to the
     computer's or terminal's serial port with the RS-232
     cable described earlier in this chapter.  Attach the
     appropriate connectors to the modem and to the serial
     port.

     NOTE:  To prevent overheating, do not cover the vents
     on the top of the modem case.

TESTING THE INSTALLATION
------------------------------------------------------------

Use the following procedures to verify that your modem is
working properly.

1.   Turn on your computer or terminal and clear the screen.
     Then turn the Courier's power switch ON.  The following
     front panel indicators, or LEDs, will light up.
     
     CD   Carrier Detect, if you have set DIP switch 6 ON,  
          enabling the CD override
     TR   Data Terminal Ready, if you have set DIP switch 1
          ON, enabling the DTR override
     MR   Modem Ready/Power ON
     CS   Clear to Send

     For more information on the front panel indicators, see
     Appendix B in the.

2.   If you're using a personal computer, load your software
     to start the program.  Set your terminal or software to
     19.2K bps or 9600 bps.  In addition, set a word length
     of either 7 bits plus 1 parity bit, or 8 bits with no
     parity--it doesn't matter which now--and 1 Stop bit.

3.   If your software allows, perform the function that lets
     you send AT commands to the modem, that is, puts the
     computer in Terminal mode.  Some communications
     programs do this automatically upon loading.  Others
     require you to display a communications or terminal
     screen, type a Function key, or perform some other
     operation.

     If necessary, review your communications software docu-
     mentation for instructions.

4.   Check to see if your computer or terminal and modem are
     communicating with each other by sending the following
     attention command.  Type either upper or lower case
     letters, not a combination, and then press the Enter
     (Carriage Return) key, shown in the example below
     between angle brackets.  (Don't type the angle
     brackets.)
          AT <Enter>

     If everything is correct, the modem responds as        
     follows:
          OK

     NOTE:  The modem is shipped with DIP switch 4 OFF,
     causing the modem to display (echo) your keyboard
     commands.  If your entered command is not displayed,
     your local echo is OFF.  To turn the local echo ON,
     send the modem the following command.
          ATE1 <Enter>

     If double characters appear on the screen, both your
     modem and software are set to local echo ON.  Either
     set your software to local echo OFF, or turn the
     modem's echo OFF with the following command.
          ATE0 <Enter>

TROUBLESHOOTING
------------------------------------------------------------

If no OK appears on your screen, review the following
checkpoints.

a.   Make sure you type all upper or lower case letters and
     press <Enter>.

b.   Check to see that you set your communications software
     to the correct serial port.

c.   Make sure your software has put the computer in
     Terminal mode, so that you can send the modem commands.
     Then review Step 4, above.

d.   Be sure that DIP switches 1 and 6 are set ON or OFF
     according to your terminal or software requirements.
     The table in Appendix B explains each function, and you
     may also need to review the STOP guide or your terminal
     or communications software documentation .

e.   The Quad switch on the right should be in the OFF      
     position.

f.   If you set DIP switch 8 OFF, for Dumb mode, reset the  
     modem to Smart mode:  reset DIP switch 8 to ON.

g.   DIP switch 3 controls the display of the modem's result
     codes, including the OK result.  The modem is shipped  
     with DIP switch 3 ON, enabling the result codes.  If   
     DIP switch 3 is OFF, reset it to the ON position.  Then
     initiate the new switch setting with the following     
     reset command.
          ATZ <Enter>

5.   A final check of the modem is to see that it gets a
     dial tone.  Type the following manual Dial command:
          ATD <Enter>

     On receipt of the command, the modem goes off hook and
     waits for a dial tone.  The OH indicator lights, and
     you'll hear the dial tone from the modem's speaker.  To
     cancel the operation, press any key.

     If you don't hear the dial tone, first increase the
     volume by sliding the volume control switch towards the
     front of the modem.  If that doesn't work, check to see
     that the phone cable from the wall jack is connected to
     the jack that has a wall jack, and not the phone, icon.
     If necessary, reconnect the phone cable correctly.
     Then try the manual Dial command again, ATD <Enter>.






























+----------------------------------------------------------+
|                                                          |
|   Chapter 3.  Data Mode Operations                       |
|                                                          |
+----------------------------------------------------------+

     The information in this chapter applies to asynchronous
     calls only.  For synchronous operations, refer to
     Appendix E.

     Detailed command descriptions are in this chapter.
     Additional command summaries are on the bottom panel of
     the modem and in the Quick-Reference Card.

COMMAND SET USAGE
------------------------------------------------------------

     The Courier command set enables you to send the modem
     two kinds of instructions:
     #    operations, such as dialing or hanging up
     #    configurations, such as enabling error control or
          data compression

     Follow these guidelines:
     1.   Your software must be loaded and your computer or
          terminal must be in Terminal mode.

          In Terminal mode the computer acts as if it were a
          standard terminal such as a teletypewriter, rather
          than a data processor.  Keyboard entries go
          directly to the modem, whether the entry is a
          modem command or data to be transmitted over the
          phone lines.  Received data is output directly to
          the screen.  The more popular communications
          software products place the computer in terminal
          mode when the software is loaded.

     2.   Type commands in either upper or lower case, not a
          combination.

     3.   All commands except A/, A> and +++ are preceded by
          the AT prefix and are executed with the
          Enter/Carriage Return key (<Enter>).

     4.   Command length = 40 characters maximum.  The modem
          doesn't count the AT prefix, Carriage Return
          character, or spaces.  It counts but doesn't act
          on punctuation such as hyphens and parentheses.

     5.   A missing numeric parameter is assumed to be zero,
          as in the command to hang up:  ATH <Enter> is the
          equivalent of ATH0 <Enter>.


          Example (spaces are not required, but are added
          here for readability):
          AT &K3 X2 DT 071 312 1234 <Enter>

Meaning:
     AT     Get ready to execute the following commands.
     &K3    Disable MNP5 data compression, use only V.42 bis
            compression.
     X2     Use the X2 result code subset.
     DT     Dial the following phone number using tone
            dialing.
     <Enter> Execute the commands.

     This chapter groups related commands into the following
     categories.

     #    Basic Commands
     #    Dialing/Answering
               Dialing
               Dial Options
               Store Phone Numbers
               Redialing
               Answer Mode
               Auto Answer
               Hanging Up
     #         Setting/Using Defaults
               Resetting the Modem
     #    Configuration:
               Echo/Speaker
               Result Codes
               Modulation
               Error Control/Data Compression
               Data Rates
               RS-232 Signal Operations
               Flow Control
     #    S-Registers
     #    Inquiry and Help
     #    Testing
     #    International Calls
     #    Miscellaneous Commands
     For an alphabetical listing of commands, check the
     first page of the index.

     NOTE:  The defaults listed are based on the modem's
     shipping configuration:  load from nonvolatile random
     access memory (NVRAM), DIP switch 10 OFF, which is the
     same as the &F1 configuration template).  For a
     complete listing of default configuration templates,
     see Appendix B.





BASIC COMMANDS
------------------------------------------------------------

AT   Attention command prefix.  Use AT alone to test for the
     OK result code.  AT must prefix all commands except A/,
     A> and +++.

Any  Terminate the current dialing operation resulting from
key  an issued Dial command; terminate Repeat mode (> or
     A>).

DIALING/ANSWERING
------------------------------------------------------------

Dialing
-------
Dn   Dial the specified phone number; also execute Dial
     options.

     The maximum number of characters allowed is 36,
     including the AT prefix, punctuation and spaces.  The
     Carriage Return (Enter key) isn't counted as a
     character.

     NOTE:  With the exception of the following Dial
     options, the modem ignores any commands issued after D
     in the same command string.

Dial Options
------------
     D    Dial the number that follows and enter Originate
          mode.

Optional parameters:
     P    Pulse dial (Default).

     T    Tone dial.

     ,    (Comma) Pause for 2 seconds before continuing to
          dial.

     ;    Return to Command mode after dialing.  If your
          phone is plugged into the modem, you can use this
          option to have the modem Auto Dial a telephone
          rather than a modem.  The Courier dials, remains
          off hook and returns the OK message, indicating it
          is in Command mode.

          For example, to have the modem place a voice call,
          enter the Dial command with a semicolon:
               ATDT5551234; <Enter>

          When the modem returns the OK result, pick up your
          phone receiver so you can talk to the other party,

          and send the command that hangs up the modem:
               ATH <Enter>

     "    Dial the letters that follow (in an alphabetical
          phone number).  NOTE:  If you are including
          another command after the dial string, use closing
          quotation marks before the additional command.

     !    Transfer a call (flash the switch-hook).  This
          command applies to modems in installations where
          other modems share the phone line.  The modem
          flashes the switch-hook (goes off hook 0.5
          seconds, on hook for 0.5 seconds and off
          hook again) to dial the specified extension.

     W    This command is useful in situations where you
          must wait for a second dial tone before continuing
          dialing.  For example, if you need to dial for an
          outside line, the Courier continues dialing as
          soon as it detects the next dial tone.
               AT DT 9 W 5551234 <Enter>

          NOTE:  This command executes only if result code
          option X3 or greater has been issued.  If the
          modem is set to X2 or lower, the modem interprets
          the W as a comma (two-second pause).

     @    Wait for an answer (with X3 or higher).  Some
          online services answer the phone and return a
          tape-recorded request for information before
          processing transactions.  In such instances, the @
          command can be used in the Dial string to tell the
          modem to detect at least one ring, wait for five
          seconds of silence at the other end of the call,
          and then continue to execute the Dial string.

          To use the @ command, set the modem to X3, X4 or
          X7.  If the modem is set to X2 or lower, the modem
          returns an ERROR message when encountering the @
          character in a command string.  If set to X5 or
          X6, the modem hangs up when it detects a voice
          answer and sends the VOICE result code.

     /    A slash (/) causes a pause of only 125
          milliseconds.

     R    Reverse frequencies.  This command allows calls to
          an originate-only modem.  It reverses the modem's
          originate/answer frequencies, forcing the Courier
          to dial out at the answer frequency.  The command
          follows the Dial command, before or after the
          phone number:
               AT D1234567R <Enter>

     X2-X7   Adaptive dialing.  When any of the X2 through
          X7 options is in effect and you do not issue a
          dialing type in the Dial string, the Courier uses
          tone dialing, which is faster than the default
          pulse type.  However, if the phone company's
          central office does not have tone detection
          equipment, the modem cannot break dial and
          continues to detect the dial tone.  If this
          occurs, the modem automatically reverts to pulse
          dialing.

DL   Dial the last-dialed number.  The modem stores each
     Dial command until it receives the next Dial command.
     Use DL instead of A/, described on the next page, if
     you wish to send the modem non-Dial commands before
     dialing again.

DSn  Dial the number stored in nonvolatile random access
     memory at position n, where n = 0-9.

Store Phone Numbers
-------------------
&Zn=s This command stores up to ten numbers, where n is the
     position 0-9 in nonvolatile memory, and s is the phone
     number string.  The number-string may be up to 36
     characters long, including any Dial command options.
               AT &Z2=555-6789 <Enter>

     Do not include modem settings in the &Zn string.  If
     the call requires a special setting, insert it in the
     command string before the DSn command.  In the
     following example, &M0 (no error control) is inserted
     before the Dial command:
               AT&M0 DS2 <Enter>

     NOTE:  The &Zn=s command functions differently when
     Dial Security is enabled.  See Appendix C for more
     information.

&Zn? Display the phone number stored in NVRAM at position n
     (n = 0-9).

Cancel Dialing
--------------
     To cancel Dial-command execution, press <any key>. If
     you inadvertently hit a key on the keyboard while the
     modem is dialing, the call is canceled.  If this
     occurs, type the A/ command explained under Automated
     Redialing later.

     When the modem receives a command, it stores the
     instruction in its command buffer until it receives the
     next AT command.  Note that if you've sent the modem an
     additional command since the Dial command, A/ re-
     executes that command instead of redialing.

Redialing
---------
A/   Re-execute the last issued command.  A/ doesn't take
     the AT prefix or a Carriage Return, and can be used to
     redial.
               A/

Automated Redialing (>, A>)
---------------------------
     While > and A> can be used to continuously repeat any
     command, they are designed for automated redialing.

Enter Repeat Mode
-----------------
>    If you know the modem you are calling is frequently
     busy, include the Repeat command in the Dial string, as
     follows:
               AT > DT 1234567 <Enter>  or
               AT DT 1234567 > <Enter>

     The modem enters Repeat mode, dials the number, waits
     60 seconds for a carrier (default), and hangs up.  Then
     after a two-second pause, it redials.

     The cycle continues until the modems connect or the
     modem reaches a maximum of 10 attempts.  The 10-try
     limit is mandated by the Canadian Department of
     Communications (DOC) to prevent tying up local
     telephone company exchanges with unconnected calls.

A>   This command combines the features of both the A/ and >
     commands.  The modem enters Repeat mode as described
     above, and redials the Dial string in the command
     buffer.  Like the A/ command, A> does not take the AT
     prefix or a Carriage Return.

Exiting Repeat Mode
-------------------
     Should you use > or A> with a command other than a Dial
     string, abort the cycle by pressing <any key>.  To
     abort automated redialing, be sure to press <any key>
     when the result code appears, during the pause before
     the modem begins dialing again.  If you press <any key>
     while the modem is dialing, that dial attempt is
     canceled but the cycle continues.

Answer Mode
------------
Force Answer Mode
A    Force Answer mode when the modem hasn't received an
     incoming call.

Auto Answer
     The Courier is shipped with DIP switch 5 ON, Auto
     Answer suppressed.  To set the modem to automatically
     answer incoming calls, do one of the following:

     1.   Before powering on the modem, set DIP switch 5
          OFF.  When you turn the computer on, the modem
          answers incoming calls on the first ring.

     2.   When the modem is on, set your communications
          software to enable auto answer.  The following
          command instructs the modem to answer on the first
          ring.  (You can substitute a higher value.  See
          the S-Register summary in Appendix B.)
               AT S0 = 1 <Enter>

          When the modem senses a call coming in, it sends
          the result code RING to your screen, goes off
          hook, and sends the remote modem a high-pitched
          answer tone.  If there is no Carrier Detect within
          60 seconds, the modem hangs up. If the connection
          is made, the modem sends a CONNECT result code.

          When the call is disconnected by you or the remote
          user, the modem hangs up and returns the NO
          CARRIER code.

          NOTE:  If DIP switch 5 is OFF and S0=0, the Auto
          Answer will be disabled.  Be sure that S0=1+256.

Suppressing Auto Answer
-----------------------
          To disable Auto Answer, reverse Steps 1 or 2
          above.  Set DIP switch 5 ON before powering on the
          modem, or set the modem to answer on zero rings
          with the following command.
               AT S0 = 0 <Enter>

Points to Remember
------------------
     1.   If the modem is attached to a computer, you can
          set the modem to receive calls when you're not at
          your computer.  Load your communications software
          as you normally do, and set the modem to Auto
          Answer.  Also set your software's file-save
          function to save incoming messages and/or files.

     2.   If you've attached your phone so it can be used
          for conventional calls, disable Auto Answer when
          you are not expecting incoming data calls.
          Otherwise, your modem may answer the phone before
          you do, greeting a voice caller with a high-
          pitched, irritating answer tone.
Hanging Up
----------
Hn   On/off hook control.

     H0   Hang up (go on hook).

     H1   Go off hook.

     +++  Escape code operations.  Once the modem is online
          to another system, the only command it recognizes
          is an escape code of three typed pluses, which
          forces the modem back to Command mode.  Do the
          following when issuing the command:

     #    Wait one second after sending the last item of
          data
     #    Type: +++
     #    Wait one second before typing any data

     Do not type the AT prefix or a Carriage Return.  The
     guard time of one second before and after the code
     prevents the modem from misinterpreting the occurrence
     of +++ in the transmitted data stream.

     If necessary, the character used in the escape code or
     the duration of the guard time can be changed by
     resetting Register S2 or S12.  See the S-Register
     Summary in Appendix B.

     In response to +++ the modem returns to Command mode.
     However, it keeps the line open or hangs up, depending
     on the setting of DIP switch 9:

     DIP Switch 9   Response to +++
     -------------------------------------------------------
     OFF            Modem goes on hook (hangs up), sends NO
                    CARRIER result code (factory setting)
     ON             Modem maintains connection (Online-
                    Command mode), sends OK result code

     The factory setting (OFF) forces an automatic
     disconnect when you issue +++.   An advantage of this
     is that you are not likely to inadvertently run up an
     all-night phone bill.

     Set DIP switch 9 ON if you want the modem to respond to
     +++ by entering Online-Command mode, enabling it to
     execute commands and return online.  (See the O
     command, below.)

     WARNING:  For unattended modem operations:  in rare
     instances, the modem may fail to recognize the +++
     escape code sequence.  If you are running the modem
     under software control for unattended operations, we
     suggest you use the surefire method of dropping the DTR
     signal from the computer or terminal for at least 50
     milliseconds, to ensure against costly phone charges.
     Methods of turning the DTR signal off--for example,
     closing the communications port--differ from one
     computer to another.

Returning Online
----------------
On   If DIP switch 9 is ON (on detection of the escape code
     the modem maintains the connection), you can issue
     commands and then toggle the modem back online with the
     On command, as in this example:
               AT Q1 O <Enter>

     There are two ways to return online.

     ATO0 Return online (normal).  (Used in the example
          above.)

     ATO1 Return online and retrain.  Use to have the modem
          re-synchronize if there were errors in a non-ARQ
          data transfer.

Hanging Up
----------
     If DIP switch 9 is ON, the escape code forces the modem
     back to Command mode but leaves the line open.  If you
     want the modem to hang up, issue the following command
     once the modem sends the OK result code.
               ATH <Enter>

     If DIP switch 9 is OFF, the modem automatically hangs
     up on receipt of the escape code.

SETTING/USING DEFAULTS
------------------------------------------------------------

     The modem's read-only memory (ROM) permanently stores
     the modem's four factory template settings.  The
     inclusion of nonvolatile random access memory (NVRAM)
     allows you to save one of these four templates, or add
     your own modifications, and write all the settings to
     NVRAM as your power-on defaults.

&Fn  The modem is shipped with four configurations
     (templates), &F0+&F3, stored in permanent
     nonprogrammable memory (ROM).  Appendix B includes
     configuration listings for each template.  Any one of
     the templates may be loaded into current memory (AT
     &Fn) or written to nonvolatile memory and reset default
     (AT &Fn &W).  Note, however, that &F0 is always loaded
     into memory if DIP switch 10 is ON.

     When you power on the Courier, it loads the settings
     stored in NVRAM if DIP switch 10 is OFF.  Until you
     write your own settings to NVRAM, the defaults stored
     there are the same as the permanent ROM factory
     settings stored in position 1, &F1.

     To view the &F1 settings, select option 5 of the I
     (inquiry) command:
               AT I5 <Enter>

Customizing NVRAM
------------------
&W   To substitute a template other than &F1, write the
     desired template to NVRAM, using the &W command.
               AT &F2 &W <Enter>

     To modify the &Fn configuration in NVRAM, type your
     changes and then save them to NVRAM, as in the
     following example.  The original factory template
     remains intact.
               AT M2 S10=40 &A2 &W <Enter>

     NOTE:  When writing a different default configuration
     to NVRAM, insert your addition after the &Fn command
     but before &W.  Otherwise they will be overwritten by
     &Fn.

     After sending a configuration to NVRAM, you can change
     any setting just for the current session, as in the
     following example.  The NVRAM configuration remains
     intact.
               ATX6 <Enter>

     But if you want the new setting to be a default, write
     it to NVRAM at the same time, as in the following
     example.  X7 is substituted for the Xn value stored
     earlier.  Any other setting that was changed and can be
     saved to NVRAM will also be saved.
               AT X7 &W <Enter>

Resetting the Modem
-------------------
Z    Software reset to NVRAM settings when DIP switch 10 is
     OFF (factory setting).  If DIP switch 10 is OFF, the
     modem resets to the &F0 configuration template, with no
     flow control.

     NOTE:  Use the ATZ command also if you've changed the
     position of DIP switches 1+7 or 9 while the modem is
     on, so that the modem can read the new setting.  The
     only other way to initiate a new setting for switches
     1-7 and 9 is to turn the modem off and on again.


CONFIGURATION
------------------------------------------------------------

Echo/Speaker
------------
En   Command mode local echo.  Enables/disables the display
     of your typed commands.  If double characters appear on
     the screen, both the modem's local echo and your
     software's local echo are on.

     The Courier is shipped with DIP switch 4 OFF, enabling
     local echo.  The En command controls the local echo for
     a current session, independently of the switch setting.
     At power-on and reset, the modem operates according to
     the DIP switch setting.  The En command is not stored
     in nonvolatile memory as a power-on/reset default.

     E0   Command mode echo OFF.  The modem does not display
          keyboard commands.

     E1   Command mode echo ON.

Fn   Online local echo.  This command causes the modem to
     display a copy of the data it is transmitting to
     another system.  Many systems, however, return a copy
     of received data, which is called a remote echo.  If
     the modem's online echo is ON and there is also remote
     echoing, double characters appear on the screen.

     In some microcomputer documentation, the term duplex is
     applied to local online echoing, although the term is
     not technically accurate.

     F0   Online echo ON.  Sometimes called half duplex.  As
          the modem transmits data to a remote system, it
          also sends a copy of the data to the screen.

     F1   Online echo OFF.  Sometimes called full duplex.
          Default.

Mn   Speaker (audio monitor).

     M0   The speaker is always OFF.

     M1   The speaker is ON until carrier is established
          (Default).

     M2   The speaker is always ON, including during data
          transfer.

     M3   The speaker is ON after the last digit is dialed
          and remains ON until carrier is established.


Result Codes
------------
Qn   Enable/suppress the display of result codes.  The
     Courier is shipped with DIP switch 3 ON, to display
     result codes.  Use the Qn command to control the
     display for a current session, independently of the
     switch setting.

     At power-on and reset, the modem operates according to
     the DIP switch setting.  The Qn command is not stored
     in nonvolatile random access memory.

     Q0   Result codes displayed.

     Q1   Result codes suppressed (quiet).

     Q2   Result codes suppressed in Answer mode.

Vn   Return result codes in words or numbers (Verbal/Numeric
     mode). At power-on and reset, the modem operates
     according to the DIP switch setting.  The Vn command is
     not stored in nonvolatile memory as a power-on/reset
     default.

     V0   Numeric mode.

     V1   Verbal mode.



























Xn   Result code set options.  Use the following table
     (Default = X7, all codes except 12/VOICE).  For result
     codes in synchronous operations, see Appendix I.

          Setting
Result Codes   X0   X1   X2   X3   X4   X5   X6   X7
----------------------------------------------------------
0/OK           *    *    *    *    *    *    *
1/CONNECT      *    *    *    *    *    *    *    *
2/RING         *    *    *    *    *    *    *    *
3/NO CARRIER   *    *    *    *    *    *    *    *
4/ERROR        *    *    *    *    *    *    *    *
5/CONNECT 1200      *    *    *    *    *    *    *
6/NO DIAL TONE           *         *         *    *
7/BUSY                        *    *    *    *    *
8/NO ANSWER                   *    *    *    *    *
9/RESERVED
10/CONNECT 2400     *    *    *    *    *    *    *
11/RINGING                              *    *    *
12/VOICE                                *    *
13/CONNECT 9600     *    *    *    *    *    *    *
18/CONNECT 4800     *    *    *    *    *    *    *
20/CONNECT 7200     *    *    *    *    *    *    *
21/CONNECT 12000    *    *    *    *    *    *    *
25/CONNECT 14400    *    *    *    *    *    *    *
43/CONNECT 16800    *    *    *    *    *    *    *
85/CONNECT 19200    *    *    *    *    *    *    *
91/CONNECT 21600    *    *    *    *    *    *    *

Functions
Adaptive Dialing         *    *    *    *    *    *
Wait for 2nd Dial Tone (W)    *    *    *    *    *
Wait for Answer (@)           *    *    *    *    *
Fast Dial                *         *         *    *

               Table 3-1.  Result Code Options

NOTE:  Additional messages indicate an error control
connection and the modulation for a call.  See the
Additional Result Codes that follow.














Result Code    Meaning
------------------------------------------------------------
0/OK           Command has been executed.
1/CONNECT      Connection with another modem; if set to X0,
               connection may be between 300 and 21.6 bps;
               if X1 or higher, connection is at 300 bps.
2/RING         Incoming ring detected.
3/NO CARRIER   Carrier detect has failed or carrier has been
               dropped due to disconnect.
4/ERROR        Command is invalid.
5/CONNECT 1200 Connection with another modem at 1200 bps.
6/NO DIAL TONE Dial tone not detected during the normal 2
               seconds, set in Register S6.
7/BUSY         Busy signal detect; modem hangs up.
8/NO ANSWER    After waiting 5 seconds for an answer, modem
               hangs up; returned instead of NO CARRIER when
               the @ option is used.
10/CONNECT 2400   Connection with another modem at 2400 bps.
11/RINGING     The modem has dialed; remote phone line is
               ringing.
12/VOICE       Voice answer at remote site; modem hangs up.
13/CONNECT 9600   Connection at reported rate.  Same
               meaning for results of 4800 (18), 7200 (20),
               12K (21), 14.4K (25), 16.8K (43), 19.2K (85),
               or 21.6K (91).

Adaptive Dialing  The modem attempts to use tone dialing
               and, if that doesn't work, reverts to rotary
               dialing.

Wait for Another  The modem continues dialing as soon as
Dial Tone (W)  it detects another dial tone.  See the
               dial options earlier in this chapter.

Wait for an    The modem continues dialing when it detects 5
Answer (@)     seconds of silence on the line.  See the dial
               options earlier in this chapter.

Fast Dial      The modem dials immediately on dial-tone
               detect, instead of waiting the normal 2
               seconds set in Register S6.

               Table 3-2.  Result Code Definitions











ADDITIONAL RESULT CODE SUBSETS
------------------------------------------------------------

     NOTE:  ARQ (Automatic Repeat Request) is used in this
     manual to denote calls under error control.

&An  Enable/disable additional result code subsets.  See the
     Xn command earlier in this chapter.

     &A0  ARQ result codes are disabled.  This setting does
          not affect an error control connection; the modem
          returns the standard CONNECT messages if result
          codes are enabled.

     &A1  ARQ result codes are enabled, indicating that a
          connection is under error control.  Message 14 is
          displayed if the modem is set to X0 and the
          connection is at any rate from 1200 to 21.6K bps.
          The remaining results indicate the connection rate
          and require a setting of X1 or higher.

     14/CONNECT/ARQ      24/CONNECT 7200/ARQ
     15/CONNECT 1200/ARQ 26/CONNECT 14400/ARQ
     16/CONNECT 2400/ARQ 47/CONNECT 16800/ARQ
     17/CONNECT 9600/ARQ 88/CONNECT 19200/ARQ
     19/CONNECT 4800/ARQ 94/CONNECT 21600/ARQ
     22/CONNECT 12000/ARQ

     &A2  Additional HST or V32 modulation indicator.
          Included for users of HST Dual Standard modems.
          If your software cannot handle the added
          modulation information, select &A1 or &A0.

     23/CONNECT 9600/HST      or   33/CONNECT 9600/V32
     27/CONNECT 9600/ARQ/HST  or   37/CONNECT 9600/ARQ/V32
     28/CONNECT 4800/HST      or   38/CONNECT 4800/V32
     29/CONNECT 4800/ARQ/HST  or   39/CONNECT 4800/ARQ/V32
     30/CONNECT 7200/HST      or   40/CONNECT 7200/V32
     34/CONNECT 7200/ARQ/HST  or   44/CONNECT 7200/ARQ/V32
     31/CONNECT 12000/HST     or   41/CONNECT 12000/V32
     32/CONNECT 12000/ARQ/HST or   42/CONNECT 12000/ARQ/V32
     35/CONNECT 14400/HST     or   45/CONNECT 14400/V32
     36/CONNECT 14400/ARQ/HST or   46/CONNECT 14400/ARQ/V32
     53/CONNECT 16800/HST     or   83/CONNECT 16800/V32
     57/CONNECT 16800/ARQ/HST or   84/CONNECT 16800/ARQ/V32
     88/CONNECT 19200/ARQ     or   87/CONNECT 19200/V32
                              or   90/CONNECT 19200/ARQ/V32
     94/CONNECT 21600/ARQ     or   93/CONNECT 21600/V32
                              or   96/CONNECT 21600/ARQ/V32

     &A3  Additional error control indicator (LAPM, HST,
          MNP, SYNC, or NONE) and data compression type
          (V42BIS or MNP5).  Default.  When the call is not
          under one of those protocols (and ARQ is not
          included in the result code), the modem reports
          either SYNC, indicating a synchronous connection,
          or NONE, for no protocol.

          If the modems are using data compression, the type
          of compression, V42BIS or MNP5, is added to the
          result code.  In the first of the following
          examples, the modems negotiated error control for
          the call (ARQ), used V32 modulation, are using the
          LAPM error control protocol, and are using V.42
          bis compression.

     CONNECT 21600/ARQ/V32/LAPM/V42BIS  [or MNP/MNP5]
     CONNECT 19200/ARQ/V32/LAPM/V42BIS  [or MNP/MNP5]
     CONNECT 19200/SYNC
     CONNECT 16800/ARQ/V32/LAPM/V42BIS  [or MNP/MNP5]
     CONNECT 16800/ARQ/HST/HST/V42BIS  [or MNP/MNP5]
     CONNECT 16800/SYNC
     CONNECT 14400/SYNC
     CONNECT 12000/ARQ/HST/HST/CELLULAR/V42BIS  [or MNP5]
     CONNECT 12000/SYNC
     CONNECT 9600/SYNC
     CONNECT 2400/ARQ/MNP/MNP5  [or LAPM/V42BIS]
     CONNECT 2400/NONE

     NOTE:  Although these codes will return numeric identi
     fiers, they are the same numeric identifiers used for
     &A2 result codes.  If the modem is in Numeric mode (V0)
     and set to &A3, you will not be able to differentiate
     between &A2 and &A3 result codes.  &A3 result codes may
     not be compatible with some software.

Modulation
----------
Bn   Handshake options.  There are three commands that apply
     to international calls above 1200 bps--Bn, &Gn, &Pn.
     See International Calls later in this chapter for
     information on the other two settings.

     B0   ITU-T (formerly CCITT) answer sequence.  Default.
          This is required to answer all V.32-type calls as
          well as calls from overseas.

     B1   Bell answer tone.  This setting selects HST
          modulation in Dual Standard modems; but should
          only be used if the modem is not required to
          answer V.32-type calls, because it sends the wrong
          answer tones.  NOTE:  This setting is used for HST
          cellular calls.





Error Control/Data Compression
------------------------------

&Mn  Enable ARQ (error control) or synchronous protocols.
     Both your modem and the remote modem must use the same
     protocol.

     &M0  Normal mode, no error control.  Due to the nature
          of phone line channels, this is never recommended
          for calls above 2400 bps.

     &M1  This setting is exclusive of the modems' error
          control and is used only for online synchronous
          mode without V.25 bis.  See Appendix E for more
          information.

     &M2  Reserved.

     &M3  Reserved.

     &M4  Normal/ARQ mode.  Default.  If an ARQ connection
          isn't made, the modem operates in Normal mode, as
          though it were set to &M0.

          NOTE:  V.32-type modems reverting to Normal mode
          transfer data at high speeds without the
          reliability of error control.  To avoid this,
          these modems, local and remote, should always be
          set for error control.  Modems in HST mode, if
          unable to establish an error control connection,
          drop to 2400 bps.

     &M5  The modem enters ARQ asynchronous mode.  The modem
          hangs up if an ARQ connection cannot be made.

     &M6  The modem enters V.25 bis synchronous mode, using
          a character-oriented link protocol similar to
          BISYNC.  See Appendix E for more information.

     &M7  The modem enters V.25 bis synchronous mode, using
          the HDLC link protocol.

&Kn  Enable/disable data compression.

     &K0  Data compression disabled.

     &K1  Auto enable/disable.  Default.  The modem enables
          compression if the serial port rate is fixed, &B1,
          and disables compression if the serial port rate
          allows the connection rate, &B0, because
          compression offers no throughput advantage when
          the serial port and connection rates are equal:
          compression may even degrade throughput.

     &K2  Data compression enabled.  Use this setting to
          keep the modem from disabling compression.

     &K3  Selective data compression.  The modem negotiates
          only for V.42 bis compression, and disables MNP
          Level 5 (MNP5) compression.  Use this setting to
          transfer 8-bit binary files, .ZIP files, and other
          files that are already compressed.  See the note
          below.

          NOTE:  MNP5 compression is not useful when
          transferring files that are already compressed,
          such as the .ZIP files downloaded from many
          Bulletin Boards and 8-bit binary files, which
          appear to the modem to be compressed.  MNP5 tends
          to add data to the transmission so that throughput
          over the link degrades.  V.42 bis compression
          dynamically detects when data is already
          compressed and turns off until it detects that
          compression will work to advantage.  The special
          &K3 setting enables the best throughput for
          already-compressed files.

     See Throughput Guidelines and Data Compression in
     Appendix A for more information, including throughput
     to expect for different kinds of files.

Data Rates
----------
     The modem can be set to a fixed or variable serial port
     rate.  A fixed rate sets the modem for the highest
     possible throughput and provides the best performance.
     A variable rate allows the modem to switch to match the
     more limited rate on the phone connection.

     Your software must support fixed or variable serial
     port rates, and must be set to either of the two
     settings.  NOTE:  Your software may refer to these
     options with terms like locked serial port (fixed rate)
     or autobaud (variable rate).

     Most communications programs support variable rates,
     but not all software supports fixed rates.

     WARNING:  To connect above 9600 bps, the serial port
     rate must be 19.2K, 38.4K, 57.6K, or 115.2K bps.  If
     the local computer is limited to 9600 bps, V.32 terbo
     modems are limited to 9600 bps maximum, that is, V.32.
     Disable V.32 terbo modulation so that the modem does
     not switch its serial port rate up higher than 9600
     bps.  Do this by setting Register S34 to 3 (S34=3) and
     including that setting in the defaults you write to
     nonvolatile memory, as shown in Setting/Using Defaults
     earlier in this chapter.
&Bn  Serial port rate variable or fixed.

     &B0  Variable rates.  When the modem switches its
          connection rate to connect with a modem operating
          at a different rate, it also switches its serial
          port rate.  The software or terminal also switches
          serial port rates to match the connection rate.

     &B1  Fixed rate.  Default.  The modem always
          communicates with the terminal or computer at the
          rate at which you have set the terminal or
          software, regardless of the connection rate.  For
          the greatest throughput, set the serial port to
          115.2K, 57.6K, 38.4K bps for high speed calls and
          to at least 9600 bps for 2400-bps calls.

          This setting is not affected by the &N setting.
          However, the serial port rate must be equal to or
          higher than the &Nn rate.

     &B2  Fixed for ARQ calls/Variable for non-ARQ calls.
          Answer mode only.  When the modem goes off hook
          and connects in ARQ mode, it shifts its serial
          port rate up to a user-specified rate, for
          example, 38.4K bps.  If the connection is not
          under error control, the modem behaves as if it
          were set to &B0 and switches its serial port rate
          to match the connection rate of each call.

          This option is designed for installations such as
          Bulletin Boards that receive calls from a wide
          variety of modems, ranging from the very slow to
          those with the Courier's advanced design.

          To implement this feature, first set your software
          to the desired rate.  Then send the modem the AT
          &B2 [other settings] &W command.

          The modem stores the rate of the command in NVRAM
          along with the settings.  Each time it makes an
          ARQ connection, the modem checks NVRAM for the
          specified serial port rate.

          When sending subsequent configurations to NVRAM,
          be sure your software is set to your selected
          serial port rate, so that the correct rate is
          maintained.

&Nn  Connection rate variable or fixed.

     &N0  Variable rates.  Default.  The Courier
          negotiates with the remote modem for the
          highest possible connection rate, depending

          on the capabilities of the remote modem.
          This is the recommended setting, and is required
          for the Courier V.32 terbo to connect at 21.6K
          bps.  Both modems must be U.S. Robotics modems
          with V.32 terbo to make a 21.6K bps connection.

     &N1- Fixed rate.  The modem only connects if the
     &N10 remote modem is operating at the same rate.
          If not, the modem hangs up.  If you wish, you can
          filter out calls at other than a specific rate,
          for security or other reasons, by fixing the
          connection rate.

          The connection rate must always be lower than, or
          equal to, the serial port rate, never higher.

          The options are as follows.
          &N1  300 bps   &N7  12K bps
          &N2  1200 bps  &N8  14.4K bps
          &N3  2400 bps  &N9  16.8K bps (HST+to+HST or
          &N4  4800 bps       terbo+to+terbo only)
          &N5  7200 bps  &N10 19.2K bps (terbo+to+terbo
          &N6  9600 bps       only)

RS-232 Signal Operations
------------------------------------------------------------

&Cn  Carrier Detect operations.  At power-on and reset, the
     modem operates according to the setting of DIP switch
     6.  This command is not stored in nonvolatile memory as
     a power-on/reset default.

     &C0  CD override, CD always ON.

     &C1  Normal CD operations.  The Courier sends a CD
          signal when it connects with another modem and
          drops the CD when it disconnects.

&Dn  Data Terminal Ready (DTR) operations.  At power-on and
     reset, the modem operates according to the setting of
     DIP switch 1.  This command is not stored in non
     volatile memory as a power-on/reset default.

     &D0  DTR override.  The modem operates as though the
          DTR is always ON.

     &D1  Advance usage:  If issued before connecting with
          another modem, the modem can enter online command
          mode during a call by toggling DTR.  (Most
          communications software packages have a method for
          toggling DTR.)  &D1 functions similarly to the
          escape code (+++), except that this setting is
          independent of DIP switch 9.

          If DIP Switch 1 is ON (DTR override) when you
          issue the &D1 command, the DTR override is
          automatically turned off.  However, if you change
          the setting of DIP switch 1 after issuing &D1, the
          DIP switch setting takes precedence.

          Return online with the On command, or hang up with
          the Hn command.

     &D2  Normal DTR operations.  The terminal or computer
          must send a DTR signal for the modem to accept
          commands.  Dropping DTR terminates a call.

&Sn  The modem sends the computer or terminal a Data Set
     Ready (DSR) signal via the RS-232 interface.  (Data Set
     is industry jargon for modem.)  Few, if any, commercial
     communications programs require the modem to control
     DSR, &S1.  Leave the modem set for DSR overridden, &S0,
     unless you know that your installation requires a
     different setting.

     &S0  DSR is always ON (override).  Default.

     &S1  In Originate mode, the modem sends the DSR after
          it dials, when it detects the remote modem's
          answer tone.  In Answer mode, the modem sends the
          DSR after it sends an answer tone.

     &S2  This option is for specialized equipment such as
          automatic callback units.  On loss of carrier, the
          modem sends a pulsed DSR signal with Clear to Send
          (CTS) following Carrier Detect (CD).

     &S3  This is the same as &S2, but without the CTS
          following CD.

     &S4  The modem sends the computer a DSR signal at the
          same time as it sends the Carrier Detect (CD).

Flow Control
------------------------------------------------------------
     Flow control allows the modem to monitor the amount of
     data coming from the computer or the remote modem, and
     notify either end if its buffers are too full, so that
     they stop sending data for a moment.

     The modem uses either hardware or software flow
     control.  Your software and machine must support
     whichever type you select.

Hardware Control
----------------
     The modem drops the Clear to Send (CTS) signal it's
     been sending to the computer or terminal when the
     modem's buffer nears 90% capacity.  It starts sending
     CTS again when the buffer is about half full.

Software Control
----------------

     The modem sends the computer or terminal the standard
     ASCII Transmit OFF (XOFF) character, <CTRL-S>, when its
     buffer nears 90% capacity.  The  modem sends the ASCII
     Transmit ON character, <Ctrl>-Q, when the buffer is
     about half full.  ASCII definitions are as follows:

     XON      <Ctrl>-Q       (ASCII 17 Decimal, 11 Hex)
     XOFF     <Ctrl>-S       (ASCII 19 Decimal, 13 Hex)

     NOTE:  You should set your software as well to either
     hardware or software flow control.  Some programs also
     require that you turn off the type you are not using.

     The ASCII characters may be user-defined.  See
     Registers S22 and S23 in Appendix B.  That appendix
     also includes an ASCII chart.

     WARNING:  If possible, always use hardware flow
     control, the factory default.  You may lose data if
     XON/XOFF (Ctrl-S, Ctrl-Q) characters occur in the data
     stream from other sources.  They may, for example, come
     from the remote system:  an XON from the remote system,
     after your modem has sent an XOFF, can result in buffer
     overflow.

     Ctrl-S (XOFF) and Ctrl-Q (XON) characters also occur in
     binary files, and are used by Xmodem-type protocols.
     You risk having these characters misinterpreted as
     modem flow control characters and dropped from the data
     stream.

     If you cannot use hardware flow control and if you're
     transferring non-text (binary) files, or using an
     Xmodem-type protocol, disable flow control entirely
     (&H0).  In addition, be sure the modem is set to &B0
     and &N0, so that the serial port and connection rates
     are equal.

Transmit Data Buffer Sizes
--------------------------
     The Transmit Data refers to the data from the computer,
     which the modem is to transmit over the phone line.

     The size of the Transmit data buffer depends on whether
     the connection is under error control or not, as
     follows.

     #    ARQ connections:  3.25K bytes.
     #    Non-ARQ connections:  1.5K bytes, allowing use of
          error control file transfer protocols such as
          Xmodem and Ymodem without flow control.

     If bit 3 of Register S15 is turned on, the non-ARQ
     buffer size is reduced to 128 bytes, for the
     convenience of BBS operators taking calls from remote
     users of slower modems.  See S-Register Summary, S15,
     in Appendix B.

Received Data Buffer Size
-------------------------
     Received Data refers to the data the modem has received
     over the phone link, which the modem is to pass on to
     its attached computer.

     The size of this buffer remains constant at 2K bytes.

Transmit Data Flow Control
--------------------------
&Hn  This type of flow control is for data transmitted to
     the modem by its attached computer or terminal.  The
     modem monitors its buffer as data comes from the
     computer or modem.  If the buffer approaches 90%
     capacity, the modem signals the computer or terminal to
     stop transmitting.  When the modem has sent enough data
     over the link to half empty the buffer, it signals the
     computer or terminal to resume transmitting.

     &H0  Transmit Data flow control disabled.

     &H1  Hardware flow control.  Default.  Requires that
          your computer or terminal and software support
          Clear to Send (CTS) at the RS-232 interface.

     &H2  Software flow control.  Requires that your
          software support XON/XOFF signaling.

     &H3  Use both hardware and software flow control.  If
          you are unsure about what your equipment supports,
          select this option.  But keep the warning, above,
          in mind about software flow control.

Received Data Flow Control
--------------------------
     Separate commands, &Rn (hardware) and &In (software),
     control the flow of Received Data passed by the Courier
     to your computer or terminal.
     Your software and machine must support whichever type
     you select, although we recommend hardware flow
     control, if possible.



Hardware Control(&Rn)
---------------------
&R0  Delay Clear to Send Response after Request to Send
     signal (RTS/CTS delay).  The delay is required by some
     synchronous mainframes and does not apply to
     asynchronous calls.

     &R1  The modem ignores RTS.  This setting is required
          if your computer or terminal or software does not
          support RTS.

     &R2  Hardware flow control of received data enabled.
          Default.  The modem sends data to the computer or
          terminal only on receipt of the RTS signal.

Software Control (&In)
----------------------
     WARNING:  In ordinary operation, the only characters
     the modem recognizes during a call are the three pluses
     (+++) of the escape code.  But when software flow
     control is enabled, the modem also looks for <Ctrl>-S
     or <Ctrl>-Q characters.  If these characters occur in a
     file or as part of a protocol, the modem reads them as
     XON/XOFF characters and acts on them.  In some cases,
     the modem drops them from the data stream.

     &I0  Disables XON/XOFF flow control of received data.
          Default.  Recommended for non-ARQ (Normal mode)
          calls, but see &I5.  The I0 option provides
          transparency for all characters except the escape
          code sequence (+++), because at this setting the
          modem does not look for control characters.

          NOTE:  Because of the risk described in the above
          warning, the settings that follow are only
          recommended for users whose data does not include
          XON/XOFF control characters.

     &I1  The Courier acts on your typed XON/XOFF commands,
          Ctrl-S or Ctrl-Q, and passes them to the remote
          computer.  Use in ARQ mode only, but keep in mind
          that the XON/XOFF characters sent to the remote
          computer may interfere with XON/XOFF signaling
          between the remote computer and remote modem.  See
          &I2.

     &I2  The Courier acts on your XON/XOFF commands, but
          removes them from the data stream instead of
          passing them to the remote computer.  This ensures
          that the remote computer does not confuse your
          XON/XOFF characters with those from its attached
          modem.  This is the recommended setting for ARQ
          mode.

          However, if the call is not in ARQ mode, there is
          no flow control on the phone link.  If you send an
          XOFF to your modem and it stops passing data, it
          has no way to tell the remote computer and modem
          to stop sending for a while, and your modem's
          buffer may overflow.  For more reliable control in
          non-ARQ mode, see &I5.

     &I3  Hewlett Packard-Host mode.  Applies only to modems
          attached to an HP mainframe that uses the ENQ/ACK
          protocol.  Use in ARQ mode only.  See Appendix F.

     &I4  Hewlett Packard-Terminal mode.  Applies only to
          modems attached to terminals in an HP system that
          uses the ENQ/ACK protocol.  Use in ARQ mode only.
          See Appendix F.

     &I5  This setting is designed to enable flow control on
          the phone link when the connection is not under
          error control.  For this to work for you, the
          remote modem must have &I5 capability.

          In ARQ mode, a Courier set to &I5 operates the
          same as it does when set to &I2.  It acts on your
          XON/XOFF commands, but does not pass them to the
          remote system.  The error control protocol enables
          the modems to control the flow of data on the
          phone link.

          In non-ARQ mode, a Courier set to &I5 operates as
          though flow control were disabled (&I0):  it does
          not look for your typed XON/XOFF commands.
          However, it looks for XON/XOFF characters coming
          in over the phone link.  When the remote operator
          sends XON/XOFF commands, the Courier either
          resumes or stops transmitting data over the link
          and drops the characters from the data stream.

          If both modems are set to &I5, operators at each
          end can signal the remote modem to stop sending,
          thereby controlling the data flow on the phone
          link and preventing their own modem's buffer from
          overflowing.  At the computer or terminal/modem
          interfaces, the modems independently control the
          flow of data through their Transmit Data (&H)
          settings.

Guidelines
----------
     Use of software flow control may prove satisfactory if
     you're only transferring text files.  However, if
     you're transferring non-text (binary) files, or using
     an Xmodem-type protocol, disable flow control entirely
     (&R1, &I0).  In addition, set the modem to &B0 and &N0,
     so that the serial port and connection rates are equal.

S-REGISTERS
------------------------------------------------------------

     The S-Registers are used to set various timing
     parameters, redefine selected ASCII characters, and
     other configuration options.  A detailed summary of the
     S-register functions is in Appendix B.  A less detailed
     summary is in the Quick-Reference card.

Sr=n Set S-Register value:  r is any S-Register; n must be a
     decimal number between 0 and 255.

Sr.b=n Alternative command for setting bit-mapped registers:
     r is the bit-mapped register; .b is the bit; n is 0
     (off) or 1 (on).

Sr?  Query contents of register r.

INQUIRY AND HELP
------------------------------------------------------------

     The modem displays information such as the current
     modem settings, product code, and call duration.  It
     also displays summary information for every command
     that the modem supports.

     For more information on Inquiry and Help commands,
     including sample displays, see Chapter 5.

TESTING
------------------------------------------------------------

     The modem can perform a number of tests including,
     Analog Loopback, Digital Loopback, and Remote Digital
     Loopback.  These tests can be used to check the
     operations of the modem's transmitter and receiver, or
     to locate a problem with a remote modem or telephone
     channel.  Error control must be disabled for these
     tests.

     See Appendix G for more information.

INTERNATIONAL CALLS
------------------------------------------------------------

     There are three commands that apply to international
     calls above 1200 bps--Bn, &Gn, &Pn.  Bn is described
     earlier in this chapter.

&Gn  This setting applies only to overseas calls at 2400 or
     1200 bps.  British phone switching systems require the
     modem to send an 1800 Hz guard tone after it sends an
     answer tone.  Some other European phone networks
     require a 550 Hz guard tone.  Guard tones are not used
     in the United States or Canada.

     &G0  No guard tone.  This is used in the U.S. and in
          Canada (Default).

     &G1  This sets a 550 Hz guard tone, and is used in
          some European countries.

     &G2  This sets an 1800 Hz guard tone, and is used in
          the U.K., and some Commonwealth countries.  &G2
          requires the B0 setting.

&Pn  This command sets the ratio of the off-hook/on-hook
     (make/break) interval for pulse dialing.  The default
     sets the modem for use in North America.  The ratio
     must be changed if the modem is used in the United
     Kingdom and some Commonwealth countries.

     &P0  Make/break ratio, U.S./Canada:  39%/61%.  Default.

     &P1  Make/break ratio, United Kingdom, some
          Commonwealth countries:  33%/67%.

MISCELLANEOUS COMMANDS
------------------------------------------------------------

Cn   Transmitter enabled/disabled.

     C0   Transmitter disabled; receive-only condition.

     C1   Transmitter enabled (Default).

Kn   Modem clock operation:  Call-duration or Real-time
     mode.  Displayed with ATI3 and ATI6 commands.

     K0   Display current call-duration if online.  Display
          last call-duration if offline.  Default.

     K1   Return actual time at ATI3.  Clock is set using
          ATI3=HH:MM:SS K1.

&Yn  Break handling.  This command allows you to send a
     break to abort data transfer without disconnecting from
     the phone link.

     &Y0  Destructive, don't send Break.

     &Y1  Destructive, expedited (Default).

     &Y2  Nondestructive, expedited.

     &Y3  Nondestructive, unexpedited; modem sends Break in
          sequence with data received from computer or
          terminal.

     NOTE:  If the call is under MNP5 data compression,
     destructive Breaks cause both modems to reset their
     data compression tables.  When transmission resumes,
     the modems build new tables, and the result is lower
     than normal throughput.

&ZC=s Write the following command string s to NVRAM.
     The command string may be up to 30 characters long;
     spaces are not counted.  This command can be used so
     that you can call another modem without loading your
     communications software.

     After storing a command, you can program the voice/data
     switch to execute the stored command string when
     pressed.  The following example assigns a command
     string that displays the link diagnostics screen when
     you press the voice/data switch.
               AT&ZC=I6 <Enter>

     The function of the voice/data switch is determined by
     the setting of Register S32, as described in Appendix
     F.  Set the voice/data switch function to execute
     stored command string by setting Register S32 to 9 with
     the following command.
               ATS32=9 <Enter>

     Note that you can reset the voice/data switch at any
     time to one of the other available functions.
     Additionally, you can overwrite the stored command
     string with a new one at any time.

     Once you've stored your command string and set Register
     S32, all you need to do is press the voice/data switch
     whenever you want the command string executed.

&ZC? Display the stored command string.

%T   Enables the modem, when off hook, to detect the tone
     frequencies of dialing modems.  %T is meant primarily
     for use with network applications, but may also be
     integrated into certain software programs.  For
     example, %T could be used in a security program to
     identify incoming tone security codes.

     To enable %T, type ATH1 <Enter> to force the modem off
     hook.  Then type AT%T <Enter>.

     To return the modem to Command mode, press any key or
     drop the computer's or terminal's DTR signal.  The
     modem responds OK.

+----------------------------------------------------------+
|                                                          |
|    CHAPTER 4.  FAX OPERATIONS AND CALL SELECTION         |
|                                                          |
+----------------------------------------------------------+

FAX OPERATIONS
------------------------------------------------------------
Compatibility

     The Courier modem provides Group III- compatibility
     when combined with Class 1 or Class 2.0 fax software.
     In addition, the modem adheres to the following
     standards.

     NOTE:  The International Telecommunication Union
     (ITU-T) was formerly the International Telegraph and
     Telephone Consultative Committee (CCITT).

       TIA/EIA-578      Service Class 1
                        Asynchronous Facsimile DCE
                        Control Standard
       TIA/EIA-592      Service Class 2.0
                        Asynchronous Facsimile DCE
                        Control Standard
       ITU-T V.17       14.4K/12K bps
       ITU-T V.29       9600/7200 bps
       ITU-T V.27 ter   4800/2400 bps
       ITU-T V.21       300 bps

Fax Modem Guidelines
--------------------
     Fax operations require facsimile- compatible software
     that can send or receive Group III faxes.  Follow the
     instructions in your fax software manual.

     The modem's normal operating mode is Data mode.  If
     your fax software is typical, it automatically switches
     the modem to Fax mode when you run the program, and
     resets the modem to Data mode when you exit the
     program.

     If you have a problem, however, and think the modem
     may be in the wrong mode, you can use one of the
     following AT commands to manually switch the modem:

        AT+FCLASS=0 (Switch to Data mode) <Enter>
        AT+FCLASS=1 (Switch to Class 1 Fax  mode) <Enter>
        AT+FCLASS=2.0 (Switch to Class 2.0 Fax mode) <Enter>

     If you are not sure whether the modem is in Data or
     Fax mode, type the following command.
          AT+FCLASS? <Enter>
     The modem  returns a value of 0 to indicate Data mode,
     1 to indicate Class 1 Fax mode, or 2.0 to indicate
     Class 2.0 Fax mode.

     NOTE:  Whenever the fax modem is reset using the ATZ
     command, by toggling the DTR signal, or by turning the
     power off and on, the modem will be set to Data mode.

Fax Mode Flow Control Setting
------------------------------

     Many facsimile software products use software flow
     control when the modem is in Fax mode.  Throughout our
     documentation, we recommend use hardware flow control
     for Data mode (factory setting).  However, to allow
     compatibility with software products that use software
     flow control by default, U.S. Robotics fax modems now
     automatically change to software flow control when
     entering Fax mode.

FCC Notice
------------------------------------------------------------
     FCC part 68, rules regarding fax operation, has been
     amended as follows:

     Telephone facsimile machines-identification of the
     sender of the message:  It shall be unlawful for any
     person within the United States to use a computer or
     other electronic device to send any message
     via a telephone facsimile machine unless such a
     message clearly contains, in a margin at the top or
     bottom of each transmitted page or on the first page of
     the transmission, the date and time it is sent and
     an identification of the business, other entity, or
     individual sending the message and the telephone number
     of the sending machine or of such business, other
     entity, or individual.  Telephone facsimile machines
     manufactured on and after December 20, 1992 must
     clearly mark such identifying information on each
     transmitted page.

NOTES TO PROGRAMMERS
------------------------------------------------------------

     Lists of supported Class 1 fax commands and optional
     Class 2.0 commands are in the Technical Specifications
     in this manual, Appendix I.

     If you want to know more about the supported Class 1
     fax commands, refer to the standard for the Service
     Class 1 fax protocol.

        ANSI/EIA/TIA-578-1990 (EIA-578)
        Asynchronous Facsimile DCE Control Standard
        November, 1990   Approved:  October 22, 1990
     For more information on Class 2.0, refer to the       
     standard for the Service Class 2.0 fax protocol.

        ANSI/EIA/TIA-592-1993 (EIA-592)
        Asynchronous Facsimile DCE Control Standard
        May, 1993

     You can obtain copies of these standards by contacting
     Global Engineering Documents, at 1-800-854-7179.


CALL SELECTION
------------------------------------------------------------

     Courier High Speed modems now support Call Selection,
     which is a method of reporting whether an incoming call
     is Data, Fax Class 1, or Fax Class 2.0.  It is
     especially useful for Bulletin Board systems, as it
     automates recognition of different calls from multiple
     users.

     Call Selection is an optional Service Class 2.0
     feature, and is also implemented by U.S. Robotics for
     Fax Class 1 applications.

     To obtain a copy of the technical specification of
     U.S. Robotics' implementation of Call Selection for Fax
     Class 1, call our BBS at (708) 982-5092 and download
     the file CALLSEL.TXT.

     For information on implementing Fax Class 2.0 Call
     Selection, see the standard listed above.  For a list
     of the optional Fax Class 2.0 commands supported by
     U.S. Robotics, see the Technical Specifications in
     Appendix I.



















---------------------------------------------------------
                                                          
   CHAPTER 5.  QUERIES AND HELP SCREENS                   
                                                          
---------------------------------------------------------

USER INQUIRIES (In)
------------------------------------------------------------

      The Inquiry command has 9 options.  The most commonly
      used options display the following information:

         ATI3  Call duration
         ATI4  Current settings
         ATI5  NVRAM settings
         ATI6  Link diagnostics summary

     I0  The modem returns a 4-digit product code.  If you
         have a problem and call U.S. Robotics' Technical
         Support Department, you may be asked for this
         product code.

     I1  The modem performs a checksum of its read-only
         memory (ROM) and returns the result to the screen. 
         This function is used only in factory testing.  The
         modem should always read the same number.

     I2  The modem performs a test of its random access
         memory (RAM) and returns either the OK (0) or ERROR
         (4) result code, followed by OK when the test is
         completed.  You may want to use this command as a
         checkpoint if the modem appears to be
         malfunctioning.

     I3  The modem returns the duration of the last call if
         set to K0.  It displays the actual time if set to
         K1.  See the description of the Kn command in
         Chapter 3.

     I4  The modem displays its current configuration. 
        
     I5  The modem displays the configuration stored in
         nonvolatile random access memory (NVRAM).  If your
         modem connects to a  modem that has Dial Security
         and local access enabled, you cannot view the
         stored phone numbers.

     I6  During a connection, the modem monitors and stores
         information about link operations.  When the call
         is ended, you can request a diagnostic summary.
         The duration of the last call or real time is
         displayed depending on the Kn setting.

         For calls under data compression, the number of
         characters sent may be less than the number of
         octets sent, due to buffering operations.  Line
         Reversals only apply to HST-mode operations, when
         the modems switch the high and low speed channels. 
         At this time, online fallback is only reported
         Enabled in HST-mode.

         Many of the terms used in the display are self-
         explanatory except for the following:

         Octets:  Compressed data units.  If the number of
         octets is greater than the number of characters
         sent, the modems probably used MNP5 compression on
         an already compressed file, and the result was
         expanded data.

         Line Reversals:  The number of times HST-mode
         modems switched the high and low speed channels.

         Blers:  Errors in data and protocol blocks.  If
         there were many block errors, your receiver may
         have experienced problems on the line.

         Blocks Resent:  These represent blocks the remote
         modem resent due to the previous category, Blers.

         Link Timeouts:  Protocol detection problems: 
         communications were severed momentarily, and the
         modems probably recovered.  This does not indicate
         the retry timeout.

         Link Naks:  Negative acknowledgments (one or more
         blocks).  

         Data Compression:  Indicates the type of data
         compression negotiated for the call (V42BIS or
         MNP5) or NONE.  A V42BIS response includes the size
         of the dictionary and the maximum string length
         used, for example, 2048/32.  See Appendix A for
         more information.  

         Equalization Long/Short:  Status of S15 bit 0; long
         if bit 0=0, short if bit 0=1.  Short equalization
         applies only to HST modems.

         Fallback:  Enabled/Disabled:  indicates whether or
         not the modems negotiated online fallback during
         the connection sequence.

         Protocol:  Indicates the error control protocol
         negotiated (LAPM, HST, MNP, NONE) or SYNC for a
         synchronous call.

         Speed:  The last rates at which the
         receiver/transmitter were operating before
         disconnecting.

         Disconnect Reason:  Possible reasons the modem hung
         up are as follows:  DTR dropped:  The computer or
         terminal dropped the Data Terminal Ready signal,
         terminating the call.

         Escape code:  The operator sent the modem the +++
         escape code.

         Loss of carrier:  The modem detected loss of the
         remote modem's carrier and  waited the duration
         specified in Register S10 (default is 0.7 seconds).

         Inactivity timeout:  The modem detected no activity
         on the line for the duration specified in Register
         S19 (default is 0, timer disabled).

         MNP incompatibility:  The modem is set to &M5 and
         the remote modem does not have MNP capability, or
         there was an MNP negotiation procedure error.

         Retransmit limit:  The modems reached the maximum
         of twelve attempts to transfer a data frame without
         error.

         LD received:  The remote modem sent an MNP error
         control Link Disconnect request.

         DISC:  The remote modem sent a V.42 Disconnect
         frame.

         Loop loss disconnect:  The modem detected a loss of
         current on the loop connecting it with the
         telephone company central office.  This usually
         occurs because the remote modem has hung up:  the
         central office drops current momentarily when there
         is a disconnect at the other end of a call.  Unless
         Register S38 is set higher than zero, the modem
         immediately hangs up at loop loss.

         Unable to Retrain:  After several attempts,
         disturbances on the phone line prevented the modems
         from retraining, and they could no longer transmit
         or receive data.

         Invalid speed:  The modem is set to &N1 or higher,
         for a fixed link rate, and the remote modem is not
         operating at the same rate.

         XID Timeout:  The modems failed to negotiate the
         V.42 Detection (XID Exchange) phase.

         SABME Timeout (Set Asynchronous Balance Mode
         Extended):  The modems failed this part of V.42
         link negotiation.

         Break Timeout:  Incompatible processing of a Break
         signal occurred.

         Invalid Codeword:  The modem received an invalid
         V.42 bis (compression) frame.

         A Rootless Tree:  The modem received an invalid
         V.42 bis (compression) frame.

         Illegal Command Code:  The modem received an
         invalid V.42 bis (compression) frame.

         Extra Stepup:  The modem received an invalid V.42
         bis (compression) frame.

Dial Security Disconnect Reason:
     Possible reasons the answering modem may have hung up 
     during a Dial Security session are as follows:

         Security Abort:  The modem hung up because it
         received an invalid password three times.

         Prompting Not Enabled:  The modem hung up because
         the originating modem did not send an autopass
         password, and prompting wasn't enabled.

         No Prompting in Sync:  The originating modem did
         not send an autopass password, and the answering
         modem cannot prompt for a password in any
         synchronous mode.

         Non-ARQ Mode:  The modem hung up because the
         originating modem was set for error control and the
         answering modem was set for non-error control.

         Mode Incompatible:  The modem hung up because both
         modems were not set to the same error control
         setting.

         No Prompting in Non-ARQ:  Prompting was enabled,
         but the modem hung up because the originating modem
         was set for error control, and the answering modem
         was set for non-error control.  The answering modem
         cannot prompt when it is set for non-error control.

     I7  The modem returns a product configuration.  If you
         have a problem and call U.S. Robotics' Technical
         Support staff, you may be asked to read this
         screen.

    I10  View Dial Security Account status.  For security
         administrators only, unless local security is
         disabled, S53=0 or S53.2=0.

S-Register Query (Sr?)
----------------------
      This command allows you to view the contents of a
      particular S-Register, as in the following example
      that requests the contents of Register S0 ("On what
      ring will the modem answer?"):
             ATS0? <Enter>

Phone Number Query (&Zn?)
-------------------------
      At this command, the modem returns the phone number
      stored in NVRAM at position n, as in the following
      example that includes a sample modem response:
             AT&Z3? <Enter>
             5551234

Last-Dialed Number Query (DL?)
------------------------------
      At this command the modem displays the number stored
      in the last-dialed number buffer:
             ATDL? <Enter>

Stored Command String Query (&ZC?)
----------------------------------
      At this command the modem displays the command string
      stored in NVRAM with the &ZC=s command:
             AT&ZC? <Enter>

HELP SCREENS
------------------------------------------------------------

      Courier modems provide five Help screens:  summaries
      of the basic AT command set, extended ampersand (&)
      command set, Dial command options, S-Register
      functions, and percent (%) command set.

      NOTE:  The Help screens are not available when the
      modem makes a connection in synchronous mode:  &M1,
      &M6, or &M7.

Stop/Restart Display
--------------------
      The following command stops the display. Hold down the
      Control key and type "S":
             <Ctrl>-S

      To restart the display, use the same command or press
      any key.


Cancel Display
--------------
      Either of the following commands cancels the display.
             <Ctrl>-C
             <Ctrl>-K

Basic Command Set ($)
---------------------
      At AT$, the Courier displays a screen that shows a
      partial summary of the command set.  A second screen,
      activated by pressing any key, shows the remaining
      commands.

Extended Command Set (&$)
-------------------------
      At AT&$, the Courier displays a screen that shows a
      partial summary of the extended ampersand command set. 
      A second screen, activated by pressing any key, shows
      the remaining command set.mmands HELP Screen

Dialing (D$)
------------
      At ATD$, the Courier displays this Dial command
      summary.

S-Register Functions (S$)
-------------------------
      At ATS$, the Courier displays a screen that shows a
      partial summary of the S-Register functions.  A second
      screen, activated by pressing any key, shows the
      remaining registers.

Percent Commands (%$)
---------------------
      At AT%$, the Courier displays a screen that shows a
      partial summary of the percent command functions.  A
      second screen, activated by pressing any key, shows
      the remaining registers.
















----------------------------------------------------------
                                                          
   APPENDIX B.  SUMMARIES AND TABLES                      
                                                          
----------------------------------------------------------

CONTENTS
------------------------------------------------------------

		The RS-232 Interface, with Pin Definitions
		Front Panel Indicators
		DIP Switch Summary
		Default Settings
		S-Register Summary


THE RS-232 INTERFACE
------------------------------------------------------------
DESCRIPTION
-----------
The RS-232 interface is a standard developed by the 
Electronic Industries Association (EIA).  It defines the 
signals and voltages used when data is exchanged between a 
computer or terminal and a modem or serial printer.  Data is 
transmitted between the devices via a cable with 25-pin, 9-
pin, 8-pin or custom-built connectors.

PIN ASSIGNMENTS
---------------
The entire standard covers many more functions than are used 
in most data communications applications.  Pin assignments 
are factory set in the Courier to match the standard DB-25 
assignments in the following table.  DB-9 connectors for AT-
compatible computers should be wired at the computer end of 
the cable as shown in the DB-9 column.  If you're using an 
Apple computer, we strongly recommend that you purchase a 
Hardware Handshaking cable to get the highest possible 
reliability performance. 

									Signal Flow	
DB-25	DB-9	Circuit	Function			Computer-
									Modem
------------------------------------------------------------
1		-	AA		Chassis Ground		both directions
2		3	BA		Transmitted Data	to modem
3		2	BB		Received Data		to computer
4		7	CA		Request to Send	to modem
5		8	CB		Clear to Send		to computer
6		6	CC		Data Set Ready		to computer
7		5	AB		Signal Ground		both directions
8		1	CF		Carrier Detect		to computer	
12		-	SCF		Speed Indicate		to computer
15		-	DB		Synchronous TX* 
					Timing			to computer
17		-	DD		Synchronous RX* 
					Timing			to computer
20		4	CD		Data Terminal Ready	to modem
22		9	CE		Ring Indicate		to computer
24		-	DA		Synchronous TX*
					Timing			to modem

* Indicates Transmitter (TX) or Receiver (RX)

		Table B.1-RS-232 Interface Pin Definitions


Minimum Requirements
--------------------
Some computer/terminal equipment supports only a few of the 
RS-232 signal functions set in the Courier.  The minimum 
required for the modem to operate are as follows: 

Asynchronous Calls
------------------
	DB-25	DB-9	
	Pin		Pin		Function			
      -----------------------------------
	2		3		Transmitted Data
	3		2		Received Data
	7		5		Signal Ground
	20		4		Data Terminal Ready*

	* Required only if you have the Data Terminal Ready
	Operations switch OFF (DIP switch 1 OFF).

Synchronous Calls
-----------------
You will need all of the above functions as well as pin 15 
for Transmitter timing signals, and pin 17 for Receiver 
timing signals.  You may need pin 24, which is assigned the 
external timing source, rather than the internal (modem) 
source assigned to pin 15.  See Appendix E for more detailed 
information.

Additional Flow Control Functions
---------------------------------
If your computer and software support Clear to Send and you 
wish to use Transmit Data hardware flow control (&H1), Pin 5 
(DB-25) or Pin 8 (DB-9) is required.  

If your computer and software support Request to Send and 
you wish to use Received Data hardware flow control (&R2), 
Pin 4 (DB-25) or Pin 7 (DB-9) is required.

FOR 38.4K SERIAL PORT RATE OR HIGHER
------------------------------------
Your terminal or computer and software must support the 
115.2K, 57.6K, or 38.4K bps rate.  Make sure the RS-232 
cable is shielded.  Cables are normally six feet long, but 
longer lengths are possible.  If you encounter problems with 
signal degradation, try a shorter cable.

If you decide to build your own cable, use a low-capacitance 
cable.  To further minimize the capacitance, connect only 
those functions (pins) that your application requires.


FRONT PANEL INDICATORS
----------------------

	Symbol	Meaning		Status
	-------------------------------------------------------
	HS		High Speed	All calls above 2400 bps:  ON 
						during call progress, after
						completion of dialing; OFF
						during HST-mode link
						negotiations at 2400 bps, then
						ON during connection.  Remains
						ON after disconnect until next
						call is originated or
						answered, or the modem is
						reset. 
	AA		Auto Answer/	Answer mode only:  ON when
			Answer		your modem is in Auto Answer
						mode, and when answering a
						call; in HST-mode, goes OFF if
						the channel is reversed and
						your answering modem transmits
						at 450 or 300 bps.  Also goes
						OFF when the modem originates
						a call.  Flashes ON for
						incoming ring detect.
	CD		Carrier Detect	ON if DIP switch 6 is OFF
						(factory setting) and the
						Courier receives a valid data
						signal (carrier) from a remote
						modem, indicating that data
						transmission is possible. 
						Also ON when the CD override
						is on, DIP switch 6 ON.  
	OH		Off Hook		ON when the Courier takes
						control of the phone line to
						establish a data link.
	RD		Received Data	Flashes when the modem sends
						result codes or passes
						received data bits to the
						computer or terminal.  
	SD		Send Data		Flashes when the computer or
						terminal sends a data bit to
						the Courier.
	TR		Data Terminal	ON if DIP switch 1 is OFF
			Ready		(factory setting) and the
						modem receives a DTR signal
						from the computer or terminal. 
						Also ON when the DTR override
						is on, DIP switch 1 ON.
	MR		Modem Ready/	ON when the Courier is powered 
			Test Mode		on.  Flashes when the modems
						retrain, including online
						fallback, or while the modem
						is in Test mode.


	Symbol	Meaning		Status
	-------------------------------------------------------
	RS		Request to 	ON if your terminal or 
			Send			software supports RTS
						and sends the RTS signal.  OFF
						if the Courier is set to &R2
						(Received Data hardware flow
						control) and the computer or
						terminal lowers RTS.
	CS		Clear to Send	ON until the modem lowers CTS
						when Transmit Data hardware
						flow control is enabled (&H1,
						&H3).  Always ON during
						synchronous connections. 
	SYN		Synchronous	ON when the modem is set to
			Mode			&M1, &M6, &M7 and enters
						synchronous mode.
	ARQ/		Error Control/	Data Mode:  Automatic Repeat
			FAX			Request.  ON Fax Operations
						when the Courier is set to &M4
						or &M5 and successfully
						connects with another modem
						under error control.  Flashes
						randomly when the Courier
						retransmits data to the remote
						modem.  Fax Mode:  Flashes
						steadily to indicate fax mode.


DIP SWITCH SUMMARY 
------------------

Purpose 
-------
The DIP switches, located at the rear of the modem, are for 
adapting the modem to your equipment and personal require-
ments.  The quick-configuration guide that comes with the 
modem indicates the recommended switch settings for many 
communications software packages.  If necessary, review your 
software documentation.

Some users are able to move a single switch with a finger 
tip.  If this doesn't work for you, use a toothpick or other 
small instrument.  Do not use a lead pencil.

Operations
----------
The DIP switch settings are power-on defaults, read by the 
Courier when it is turned on.  If changed when the modem is 
on, switches 1-7, and 9 require the ATZ (software reset) 
command to initiate the new settings.  If you've set switch 
8 OFF to disable command recognition, and want to return the 
modem to Smart mode so that it responds to commands, just 
reset switch 8 to ON.

When you issue the ATZ command, the modem reads its DIP 
switch settings and resets either to its defaults (DIP 
switch 10 OFF) or factory settings (DIP switch 10 ON).

				Table B.2-DIP Switches

			Factory
	Switch	Setting	Function					
	-------------------------------------------------------
		1	OFF		Data Terminal Ready Operations 
					OFF	Normal DTR operations:  	
						computer must provide DTR
						signal for modem to accept
						commands; dropping DTR
						terminates a call
				ON		DTR always ON (Override)
					
								(continued)


			Factory
	Switch	Setting		Function					
	-------------------------------------------------------
		2	OFF			Verbal/Numeric Result Codes
						OFF	Verbal (word) results
						ON	Numeric results

		3	ON			Result Code Display
						OFF	Results suppressed
						ON	Results enabled

		4	OFF			Command Mode Local Echo
						OFF	Keyboard commands 	
							displayed
						ON	Echo suppressed

		5	ON			Auto Answer 
						OFF	Modem answers on first 
							ring
						ON	Auto answer disabled

		6	OFF			Carrier Detect Operations
						OFF	Courier sends CD signal
							when it connects with
							another modem, drops CD
							on disconnect
						ON	CD always ON (Override)

		7	OFF			Auxiliary, DIP Switch 3 ON
						OFF	Result codes in Originate
							and Answer mode
						ON	Result codes in Answer
							mode disabled

		8	ON			AT Command Set Recognition
						OFF	Command recognition 	
							disabled (Dumb mode)
						ON	Recognition enabled
							(Smart mode)

		9	OFF			Escape Code (+++) Response
						OFF	Modem hangs up, returns
							to Command mode, sends NO
							CARRIER result
						ON	Modem maintains
							connection, returns to
							Command mode, sends OK
							result

									continued


			Factory
	 Switch	Setting		Function					
	-------------------------------------------------------
		10	OFF			Power-on and ATZ Reset
						Software Defaults
						OFF	Load from nonvolatile
							memory (NVRAM)
						ON	Load factory settings
							from read only memory
							(ROM)

	QUAD		OFF			RS-232 Transmit/Receive Pin
	SWITCH				Assignments
						OFF	Normal assignments; see
							Pin Assignments earlier
							 in this appendix
						ON	Reversed Transmit/Receive
							pins

						The need to change this switch
						setting is rare.  Carefully
						review your computer or
						terminal documentation before
						setting this switch ON.
DEFAULT SETTINGS
------------------------------------------------------------

User-programmable Defaults
--------------------------
You can create your own default configuration and store it 
in nonvolatile random access memory (NVRAM) using the &W 
command described in Chapter 3.  As long as DIP switch 10 is 
OFF when you power on the modem, your defaults are loaded 
into the modem's random access memory (RAM).  To view your 
NVRAM settings at any time, use the ATI5 command.

Tables on the next several pages list the options you can 
store in NVRAM, including S-Register settings.  If DIP 
switch 10 is ON at power-on, the factory template 0 settings 
are loaded instead.  The modem has four factory setting 
templates (&F0-F3).  By default, the first time the modem is 
turned on, the modem loads the settings stored in NVRAM, 
which are the same as the settings in factory template 1 
(&F1).

The following command example substitutes several user-
defined defaults for factory settings.  The modem also 
stores the rate, word length and parity it detects from the 
AT command prefix.
		AT X1 &B0 &M5 &H0 M3 &W <Enter>


The modem is shipped with DIP switch 10 OFF, so when it is 
powered on it loads the settings from NVRAM.  Until these 
settings are changed, they are they same as the settings 
permanently stored in factory settings template 1 (&F1).  
You can alter any of these settings, create your own power-
on defaults, and then save them with the &W command.  See 
Chapter 3.  



















Table B.3-&F1 Hardware Flow Control Default Template

NVRAM Options			Setting	Description
------------------------------------------------------------
Handshake option		B0		ITU-T answer sequence
Error control/sync		&M4		Normal/error control
Data compression		&K1		Enabled
Transmit data hardware	&H1		Hardware flow control
Rec'd data hardware 
  flow control			&R2		Enabled
Rec'd data software
  flow control			&I0		Disabled
Serial port rate select	&B1		Serial port rate fixed
							higher than connect rate
Link rate select		&N0		Variable 
Result code subset		X7		Extended.  Includes all
							codes except VOICE
Protocol response codes	&A3		Full protocol codes
Tone/Pulse dialing		P		Pulse dial
Online local echo		F1		Disabled
Speaker control		M1		ON during dial through
							connect
Remote Digital 
  Loopback (RDL)		&T5		Deny RDL
Normal/Leased/
  Cellular line		&L0		Normal phone line

Data Set Ready 
  operations			&S0		Override enabled
Break handling			&Y1		Clear buffer, send
							immediately

Stored telephone number	&Z0-9=0	Blank
Pulse dial make/
break ratio			&P0		U.S./Canada
Guard tone			&G0		U.S./Canada

Word length*			8
Parity*				0		None
DTE rate* (Kbps)		19.2		-

*  Detected by the modem from the AT prefix of the &W com-
mand that writes your defaults to NVRAM.  Set your software 
to the desired word length, parity, and serial port rate 
defaults before sending the modem the AT . . . &W string.


The &F2 and &F3 factory setting templates are similar to the 
&F1, with the exception of the commands which have one 
asterisk before them in tables B.4, B.5 and B.6.




Table B.4-&F2 Software Flow Control Template

NVRAM Options			Setting	Description
------------------------------------------------------------
Handshake option		B0		ITU-T answer sequence
Normal/error control/sync     &M4	Normal/error control
Data compression		&K1		Enabled
*Transmit data 
  flow control			&H2		Software flow control
*Rec'd data hardware 
  flow control			&R1		Disabled
*Rec'd data software 
  flow control			&I2		Enabled

Serial port rate select	&B1		Serial port rate fixed
							higher than connect rate
Link rate select		&N0		Variable 

Result code subset		X7		Extended.  Includes all
							codes except VOICE
Protocol response codes	&A3		Full protocol codes
Tone/Pulse dialing		P		Pulse dial
Online local echo		F1		Disabled
Speaker control       	M1		ON during dial through
							connect

Remote Digital 
Loopback (RDL)			&T5		Deny RDL
Normal/Leased/
Cellular line			&L0		Normal phone line
Data Set Ready 
operations			&S0		Override enabled
Break handling			&Y1		Clear buffer, send
							immediately

Stored telephone number	&Z0-9=0	Blank
Pulse dial make/
break ratio			&P0		U.S./Canada
Guard tone			&G0		U.S./Canada

Word length**			8
Parity**				0	None
DTE rate** (Kbps)		19.2	-

**  Detected by the modem from the AT prefix of the &W com-
mand that writes your defaults to NVRAM.  Set your software 
to the desired word length, parity, and serial port rate 
defaults before sending the modem the AT . . . &W string.






Table B.5-&F3 HST Cellular Template

NVRAM Options			Setting	Description
------------------------------------------------------------
*Handshake option		B1		HST-mode/Bell answer tone
Normal/error control/sync     &M4	Normal/error control
Data compression		&K1		Enabled
Transmit data 
  flow control			&H1		Hardware flow control

Rec'd data hardware 
  flow control			&R2		Enabled
Rec'd data software 
  flow control			&I0		Disabled
Serial port rate select	&B1		Serial port rate fixed
							higher than connect rate
Link rate select		&N0		Variable 

Result code subset		X7		Extended.  Includes 
							all codes except VOICE.

Protocol response codes	&A3		Full protocol codes
Tone/Pulse dialing		P		Pulse dial
Online local echo		F1		Disabled
Speaker control       	M1		ON during dial through
							connect

Remote Digital 
Loopback (RDL)			&T5		Deny RDL
*Normal/Leased/
  Cellular line		&L2		HST Cellular
*Carrier loss wait time	S10=30	Tenths of seconds

Data Set Ready override	&S0		Enabled
Break handling			&Y1		Clear buffer, send
							immediately

Stored telephone number	&Z0-9=0	Blank
Pulse dial make/
  break ratio			&P0		U.S./Canada
Guard tone			&G0		U.S./Canada

Word length**			8
Parity**				0	None
DTE rate** (Kbps)		19.2	-

**  Detected by the modem from the AT prefix of the &W com-
mand that writes your defaults to NVRAM.  Set your software 
to the desired word length, parity, and serial port rate 
defaults before sending the modem the AT . . . &W string.




If DIP switch 10 is ON when the modem is powered on, or you 
load factory template 0 (&F0), the following settings take 
effect.

Table B.6-&F0 No Flow Control Template

NVRAM Options			Setting	Description
------------------------------------------------------------
Handshake option		B0		ITU-T answer sequence
Normal/error control/sync     &M4	Normal/error control
Data compression		&K1		Enabled
*Transmit data 
flow control			&H0		Disabled

*Rec'd data hardware 
  flow control			&R1		Disabled
Rec'd data software 
  flow control			&I0		Disabled
Serial port rate select	&B0		Detect from AT command:
							variable rate 

Link rate select		&N0		Variable 
*Result code subset		X1		Basic

*Error-control 
  response codes		&A1		Enabled
Tone/Pulse dialing		P		Pulse dial
Online local echo		F1		Disabled
Speaker control       	M1		ON during dial through 
							connect
Remote Digital 
  Loopback (RDL)		&T5		Deny RDL
Normal/Leased/
  Cellular line		&L0		Normal phone line
Data Set Ready 
  operations			&S0		Override enabled
Break handling			&Y1		Clear buffer, send
							immediately

Stored telephone number	&Z0-9=0	Blank
Pulse dial make/
  break ratio			&P0		U.S./Canada
Guard tone			&G0		U.S./Canada

*Word length			7
*Parity				1	Even
*DTE rate (bps)		9600	-

NOTE:  The word length, parity and DTE rate are detected by 
the modem from the AT prefix of the &W command that writes 
your defaults to NVRAM.  Set your software to the desired 
word length, parity, and serial port rate defaults before 
sending the modem the AT . . . &W string.

										Factory 
NVRAM S-Register Options 					Setting
------------------------------------------------------------
S0	Auto Answer							1
S2	Escape code character					43
S3	Carriage Return character				13
S4	Line Feed character						10
S5	Backspace character						8
S6	Dial wait-time, sec.					2
S7	Carrier wait-time, sec.					60
S8	Dial pause, sec.						2
S9	Carrier Detect time, 1/10th sec.			6
S10	Carrier loss wait-time, 1/10th sec.		7
S11	Tone duration, spacing, msec.				70
S12	Escape code guard time, 1/50th sec.		50
S13	Bit-mapped functions					0
S15	Bit-mapped functions					0
S19	Inactivity/hang up timer					0
S21	Break length, 1/100th msec.				10
S22	XON character							17
S23	XOFF character							19
S24	Pulsed DSR duration, 2/100th sec.			150
S26	RTS/CTS delay time, 1/100th sec.			1
S27	Bit-mapped functions					0
S28	V.32 handshake time, 1/10th sec.			8
S29	V.21 handshake time, 1/10th sec.			20
S32	Talk/Data Switch Options					9
S33	Bit-mapped functions					0
S34	Bit-mapped functions					0
S38	Disconnect wait time, sec.				0
S41	Allowable remote login attempts			0
S42	Remote Access ASCII character				126
S43	Remote guard time, 1/50th sec.			200
S44	Re-establish leased-line connect, sec.		15
S51	Bit-mapped functions					0
S53	Bit-mapped functions					0

*  Bit-mapped registers have up to eight functions.  See 
descriptions later in this appendix or a briefer summary in 
the Quick Reference Card.














S-REGISTER SUMMARY
------------------------------------------------------------

USAGE 
-----
The default values are those users typically require.  
Change the settings of an S-Register with the ATSr=n 
command, where r is the register and n is a decimal value 
from 0-255:
		ATS13=8 <Enter>

The modem does not perform a value-range check.  Some values 
you select may not work with some equipment, and you'll have 
to readjust the settings.  

Some registers (S13, S14, S15, S16, S27, S34) are bit-mapped 
(bits 0-7).  For example, turning on bit 0 of S13 causes the 
modem to reset each time the computer or terminal drops its 
Data Terminal Ready (DTR) signal.  Turning on bit 3 of S13 
causes the modem, on receipt of DTR, to auto dial the number 
stored at position 0 in NVRAM.

To turn on one or more bits in any bit-mapped register, use 
the total of the values shown below.  For example, S13=9 
turns on bits 0 (value of 1) and 3 (value of 8).

Alternatively, identify the bits to be turned on with the 
following format:  Sr.b=1, where r is the register and .b is 
the bit.  This format does not require knowledge of the 
bit's value.  S13.0=1 .3=1 is the equivalent of S13=9, 
above.  To turn off a bit function, set it to zero:  
S13.0=0.

To display the contents of a register, use ATSr? as in this 
example: 
		ATS1? 

To display the contents of a register, use ATSr? as in this 
example: 
		ATS19? <Enter>














Register  	Default	Function					
------------------------------------------------------------

S0			See DIP	Sets the number of rings on which 
			switch 5	to answer when in Auto Answer mode. 
					S0=0 disables Auto Answer, the same
					as DIP switch 5 ON (factory
					setting).  S0=1 enables Auto Answer
					and the modem answers on the first
					ring. 

					NOTE:  If DIP switch 5 is OFF and
					S0=0, Auto Answer remains disabled.

S1			0		Counts and stores the number of
					rings from an incoming call. 

S2			43		Stores the ASCII decimal code for
					the escape code character.  Default
					character is "+".  A value of 128-
					255 disables the escape code.

S3			13		Stores the ASCII decimal code for
					the Carriage Return character.
					Valid range is 0-127.

S4			10		Stores the ASCII decimal code for
					the Line Feed character.  Valid
					range is 0-127.

S5			8		Stores the ASCII decimal code for
					the Backspace character.  A value
					of 128-255 disables the Backspace
					key's delete function.

S6			2		Sets the number of seconds the
					modem waits before dialing.  If set
					to X2, X4, X6, or X7, the modem
					dials as soon as it detects a dial
					tone (fast dials).  If there is no
					dial tone, the modem observes the
					normal S6 timeout.

S7			60		Sets the number of seconds the
					modem waits for a carrier.  May be
					set for much longer duration if,
					for example, the modem is
					originating an international
					connection. 





Register  	Default	Function					
------------------------------------------------------------

S8			2		Sets the duration, in seconds, for
					the pause (,) option in the Dial
					command and the pause between
					command re-executions (> and A>
					commands).

S9			6		Sets the required duration, in
					tenths of a second, of the remote
					modem's carrier signal before
					recognition by the Courier.

S10			7		Sets the duration, in tenths of a
					second,  that the modem waits after
					loss of carrier before hanging up. 
					This guard time allows the modem to
					distinguish between a line hit, or
					other disturbance that momentarily
					breaks the connection, from a true
					disconnect (hanging up) by the
					 remote modem. 

					While we do not recommend
					connecting the modem to a line with
					call waiting, if you have call
					waiting you may wish to adjust this
					setting upward to prevent the modem
					from misinterpreting the signal for
					a second call as a disconnect by
					the remote modem.  A better
					alternative is to contact your
					phone company to find out how to
					temporarily disable call waiting.

S11			70		Sets the duration and spacing, in
					milliseconds, of dialed tones. 

S12			50		Sets the duration, in fiftieths of
					a second, of the guard time for the
					escape code (+++) sequence.












Register  	Default	Function					
------------------------------------------------------------

S13			0		Bit-mapped register.  Select the
					bit(s) you want on and set S13 to
					the total of the values in the
					Value column.  For example, 
					ATS13=20 enables bit 2 (value = 4)
					and bit 4 (value = 16).  Or use
					ATSr.b=0 (OFF) or 1 (ON).  For
					example, ATS13.0=1 .3=1 turns 
					on bits 0 and 3.   To turn a bit
					off, set that bit to zero, as in
					ATS13.3=0.

			Bit	Value	Result
			 0	1	Reset when DTR drops
			 1	2	Reverse normal Auto Answer
					operation:  on incoming RING, enter
					Originate Mode and look for Answer
					tone
			 2	4	Disable 250 msec. pause before
					result code display
			 3	8	On DTR signal, Auto Dial the number
					stored in NVRAM at position 0 
			 4	16	At power on/reset, Auto Dial number
					stored in NVRAM at position 0 
			 5	32	Disable HST (used for testing V.32
					terbo in Dual Standard modems)
			 6	64	Disable MNP Level 3 (used for
					testing Level 2)
			 7	128	Custom applications

S14			0		Reserved.




















Register  	Default	Function					
------------------------------------------------------------

S15			0		Bit-mapped register.  To set the
					register, see the instructions for
					S13. 
				 Bit	Value	Result
				 0	1	Disable the modem's extra
						high-frequency equalization if
						it causes problems on shorter-
						link calls--HST-modems only
				 1	2	Disable online fallback
				 2	4	Disable 450 bps back channel--
						HST only
				 3	8	Reset non-ARQ mode Transmit
						buffer from 1.5K bytes to 128* 
				 4	16	Disable MNP Level 4; retrans
						mitting the larger Level 4
						data blocks may be a problem
						if you expect a great number
						of errors during a call
				 5	32	Set backspace key to delete
				 6	64	Some earlier 2400 bps MNP
						modems, not made by U.S.
						Robotics or Microcom, were not
						fully compatible with the MNP
						protocol.  If you have
						difficulty making a successful
						2400 bps MNP connection with a
						remote MNP modem, it may be
						because of this incompati-
						bility.  Set S15 to 64 and try
						again to make the connection. 
				 7	128	Custom applications only

	* The default 1.5K byte non-ARQ buffer allows data 
	transfer with X- and Ymodem-type file transfer
	 protocols without using flow control. 

	The 128-byte option allows remote users with slower
	modems to stop data you're transmitting from scrolling
	off their screens.  When remote users send your
	computer an XOFF (<Ctrl-S>) and you stop transmitting,
	the data in transit from your modem's buffer doesn't
	exceed the size of their screen. 









Register  	Default	Function					
------------------------------------------------------------

S16			0		Bit-mapped test register.  To set
					the register, see the instructions
					for S13.  For information on
					testing, see Appendix G.

				 Bit	Value	Result
				 0	1	Analog Loopback
				 1	2	Dial test
				 2	4	Test pattern
				 3	8	Remote Digital Loopback
				 4	16	Reserved
				 5	32	Reserved
				 6	64	Reserved 

S17			0		Reserved. 

S18			0		Test timer for software-initiated
					loopback testing (&Tn), disabled
					when S18 is set to 0.  See Appendix
					G.  Used to set the duration of
					testing, in seconds, before the
					modem automatically times out and
					terminates the test.

S19			0		Sets the duration, in minutes, for
					the Inactivity Timer.  The timer
					activates when there is no data
					activity on the phone line and at
					the timeout the modem hangs up. 
					S19=0 disables the timer.

S20			0		Reserved.

S21			10		Sets, in 10-millisecond units, the
					length of Breaks sent from the
					modem to the computer or terminal. 
					Applies to ARQ mode only.

S22			17		Stores the ASCII decimal code for
					the XON character.

S23			19		Stores the ASCII decimal code for
					the XOFF character.

S24			150		Sets the duration, in 20-
					millisecond units, between pulsed
					DSR signals when the modem is set
					to &S2 or &S3.  The default is 3
					seconds.


Register  	Default	Function					
------------------------------------------------------------

S25			0		Reserved.

S26			1		Sets the duration, in 10-
					millisecond units, of the delay
					between RTS and the modem's CTS
					response in synchronous mode.  

S27			0		Bit-mapped register.  To set the
					register, see the instructions for
					S13.
			Bit	Value	Result
			0	1	Enable ITU-T V.21 modulation at 300
					bps for overseas calls.  In V.21
					mode, the modem answers both Bell
					103 and V.21 calls, but only
					originates V.21 calls.
			1	2	Enable unencoded (non-trellis-
					coded) modulation in V.32 mode;
					this option is part of the ITU-T
					V.32 recommendation, but is rarely
					used.
			2	4	Disable V.32 modulation; used for
					testing HST modulation in Dual
					Standard modems.
			3	8	Disable 2100 Hz answer tone to
					allow two V.42 modems to connect
					more quickly.
			4	16	See next page.
			5	32	See next page.
			6	64	Reserved.
			7	128	Unusual software incompatibility. 
					Some software may not accept 7200,
					12000, 14400, 16800, 19200 and
					21600 bps result codes.  This
					setting disables the codes and
					displays the 9600 code instead. 
					The call's actual rate can be
					viewed on the ATI6 screen.

						continued on following page











Register  	Default	Function					
------------------------------------------------------------

			Error control handshaking options:  select
			the total values of bits 4 and 5.  
			Bit 4	Bit 5	Result
			0		0		Complete handshaking
							sequence:  V.42
							Detection, LAPM error
							control, MNP
			16		0		Disable MNP
			0		32		Disable V.42 Detection
							and LAPM
			16		32		Disable Detection phase,
							if you know that the
							remote modem does LAPM,
							but not the Detection
							phase.

S28			8		Sets the duration, in tenths of a
					second, of the extra 3000/600 Hz
					answer tones sent during V.32 hand-
					shaking.  Default = 8 (.8 seconds). 
					This gives V.32 modems additional
					time to connect in V.32 mode before
					timing out.

					If there is difficulty answering
					older, manually operated V.32
					modems, for example, modems that
					require a button to be pushed in
					order to dial, try lengthening the
					duration of the extra tones.

					Setting S28 to zero eliminates the
					extra tones, resulting in a faster
					connect time if, for example, the
					modem is set to use V.21 modulation
					(300 bps) or V.23 modulation (1200
					bps).

S29			20		Sets the duration, in tenths of a
					second, of the answer tones sent
					during V.21 handshaking.  Default =
					20 (2 seconds).  This gives V.21
					modems additional time to connect
					in V.21 mode before timing out.

S30-S31		0		Reserved.





Register  	Default	Function					
------------------------------------------------------------

S32			9		Sets the function for the
					voice/data switch.  This is not a
					bit-mapped register.  Select the
					start value for the desired
					function, for example, ATS32=6.

		Value	Result
		0		Disabled
		1		Voice/data, Originate mode.  See bit 9.
		2		Voice/data, Answer mode
		3		Redial last number
		4		Dial number stored at position 0
		5		Auto Answer on/off toggle
		6		Reset the modem
		7		Initiate Remote Digital Loopback
		8		Busy out phone line toggle
		9		Default.  If a command string is stored
				with the &ZC=string command, and the
				voice/data switch is pushed, the modem
				executes the stored command string. 
				Otherwise the modem acts like it is set
				to bit 1, Originate mode.

S33		0		Setting this register to 1 (S33=1)
				enables HST Cellular mode.


























Register  	Default	Function					
------------------------------------------------------------

S34			0		Bit-mapped register.  See
					instructions for S13.
			 Bit	Value	Result
			 0	1	Disable V.32 bis.  Used for
					troubleshooting; U.S. Robotics'
					Technical Support may require that
					you disable V.32 bis for testing
					purposes. 	
			 1	2	Disable the modem's enhanced,
					proprietary V.32 bis modulation. 
					Used for troubleshooting
			 2	4	Disable the faster retrains that
					occur during proprietary V.32
					terbo modulation.  Used for
					trouble-shooting
			 3	8	Enable V.23.  Required for some
					British connections
			 4	16	Change MR LED to DSR
			 5	32	Enable MI/MIC; see Appendix F.
			 6	64	Disable the remote access busy
					message.
			 7	128	Disable V.32 terbo.

S35-S37		0		Reserved.



























Register  	Default	Function					
------------------------------------------------------------

S38			0		Sets the duration, in seconds,
					before a forced hang-up and
					clearing of the Transmit buffer,
					when DTR drops during an ARQ call. 
					This is provided to allow time for
					a remote modem to acknowledge
					receipt of all transmitted data. 
					Default = 0:  the modem immediately
					hangs up when DTR drops.  If the
					modem receives the ATH command, it
					ignores S38 and immediately hangs
					up.

S39-S40		0		Reserved.

S41			0		Sets the number of allowable remote
					access login attempts, thus
					enabling or disabling remote
					access.  The default setting of
					zero allows no remote login
					attempts, thus disabling remote
					access.  A value of 1 or greater
					enables remote access.  If the
					number of unsuccessful login
					attempts exceeds the limit set by
					this register, the modem returns
					online and any further login
					attempts during the remainder of
					that connection are refused.

S42			126		Stores the ASCII decimal code for
					the remote access escape character. 
					The default character is a tilde
					(~).

S43			200		Sets the duration, in fiftieths of
					a second, of the guard time for the
					remote access (~~~~) sequence.

S44			15		Sets the duration, in seconds, of
					the delay between when the modem
					senses loss of carrier and when it
					attempts to re-establish a leased-
					line connection.  

S45-S50		0		Reserved.





Register  	Default	Function					
------------------------------------------------------------

S51			0		Bit-mapped register.  See
					instructions for S13.
				Bit	Value	Result
				0	1	Disable MNP/V.42 for
						V.22 (1200 bps)
				1	2	Disable MNP/V.42 for
						V.22 bis (2400 bps)
				2	4	Disable MNP/V.42 for
						V.32/V.32 bis/V.32 terbo 
						(9600/14,400/19,200/
						21,600 bps).
				3-7	-	Reserved

S52			0		Reserved.

S53			0		Bit-mapped register.  Select the
					Dial Security features you want
					enabled by setting S53 to the total
					of the values in the Value column
					in the table below.  For example,
					S53=3, enables Dial Security with
					prompting.  S53=5 enables Dial
					Security, and local-access password
					protection.  Or use ATSr.b=0 (OFF)
					or 1 (ON).  For example, ATS53.0=1
					.2=1 turns on bits 0 and 2.  To
					turn a bit off, set that bit to
					zero, as in ATS53.2=0.

				Bit	Value	Result
				0	1	Dial security enabled
				1	2	Prompting enabled
				2	4	Local-access password
						protection enabled
			
















+----------------------------------------------------------+
|                                                          |
|   APPENDIX C.  DIAL SECURITY AND                         |
|   REMOTE ACCESS OPERATIONS                               |
|                                                          |
+----------------------------------------------------------+

Dial Security is designed to protect networks and data
centers from unauthorized access.  A system administrator is
responsible for setting up to ten Dial Security accounts in
the modem's nonvolatile memory.

WARNING:  You must set up your local access security infor-
mation before enabling Dial Security, and allowing remote
calls, as outlined under Setting Up Security, after the
overview.  Be sure to remember your local access password;
if you enable security and forget your local access
password, you risk being locked out of your system.

OVERVIEW
------------------------------------------------------------

Autopass
--------
When the calling or remote user's modem is set for Dial
Security, it requests a V.42 error correcting connection,
and automatically sends an autopass password.
In order to use Autopass, the following requirements must be
met:
#    host and remote modems must be U.S. Robotics modems    
     with Dial Security enabled.
#    a V.42 error correcting connection must be made.

Prompting
---------
Prompting allows a wider base of remote modems to connect
with the host U.S. Robotics Dial Security modem.  Instead of
sending an autopass password during the connection process,
the host modem prompts the remote user for a password.
Prompting is more flexible than autopass because it:
#    doesn't require a remote modem to have Dial Security.
#    doesn't require a V.42 connection, so remote modems    
     without V.42 error control capabilities can connect.

NOTE:  The host modem must be set for &M4 or &M5 in order to
prompt remote users.  &M4 is recommended if calling modems
do not support V.42 error control.

Optional Dialback
-----------------
Once a connection is made, the host disconnects and dials
back the remote modem at a predefined number or allows a
caller to specify a different dialback number, depending on
the security setup.
WHAT THE SYSTEM ADMINISTRATOR NEEDS TO DO
------------------------------------------------------------

Setting Up Security
-------------------

Before the system administrator activates Dial Security, the
following steps must be followed, in the listed order.
1.   Set up the system administrator's account, using one of
     the accounts numbered 0-9.  Each account has five
     possible fields, as shown in the following table.  In
     the example below, the system administrator uses the
     name BILL as a password.

Password  Account   Dialback  Allow New      Dialback
Enabled   Enabled   Enabled   Number              Number
------------------------------------------------------------

8 chars.  YES/NO    YES/NO    YES/NO         up to 37
max.                                         characters
ASCII                                        (0-9 #*,/:"!
32-127                                       PT@R)
case-
sensitive

BILL         Y         Y         N            1-419-555-5555

Use the %An= command and format below to set up accounts,
where n is the account number, 0-9.  The fields in the above
table are entered after the equal sign, each separated by a
comma, as in the following example for account 0 with the
password BILL.

WARNING:  Inserting spaces between commas or between fields
and commas will invalidate the command.
          AT%A0=BILL,Y,Y,N,1-419-555-5555 <Enter>

This example instructs the modem to store the configuration
for  account 0:  password (BILL), account enabled (Y),
dialback enabled (Y), allow a new number (N), and the
dialback phone number.

NOTE:  The %An= command is automatically written to NVRAM
and does not require an &W.

Each function can be configured or modified independently.
If a field is to remain blank, just insert a comma, as shown
in the following command which allows the remote user to
supply a new number different from the dialback number
stored in the account record.
          AT%A0=,,,Y, <Enter>

Some accounts may have fewer security options.  The
following example sets the password (Judy) and enables

account 1 without any dialback options.
          AT%A1=Judy,Y,,, <Enter>

2.   Set up your local access password.  This password,
     which protects the integrity of the accounts by denying
     access by other users, must be one of the enabled
     account passwords, and must be chosen before Dial
     Security is enabled.

The local access password is set with the %L= command.
In the following example, the local access password is the
same as the password in account 0, BILL.
          AT%L=PW0 <Enter>

3.   Enable local access password protection by turning on
     bit 2 of Register S53.
          ATS53.2=1 <Enter>

NOTE:  Once enabled, remote users cannot change the local
access password.  If local access password protection is not
enabled, remote users can get into the host modem and change
account information, including erasing all accounts.

In addition, enabling local access password protection
disables the &Zn=s command which stores up to ten phone
numbers, and occupies the same space in NVRAM as the
dialback numbers for Dial Security accounts.

If the local access password is not protected, the &Zn=s
command overwrites the corresponding Dial Security dialback
number.  For example, the following command overwrites the
dialback number for account 5.
          AT &Z5 = 555-8976 <Enter>

However, if the local access password is protected, and a
user tries to use the &Zn=s command, an ACCESS DENIED
message is displayed.

4.   Set up the remote users' accounts with the %An=
     command, using the guidelines found in step 1.

5.   Enable Dial Security, choosing either autopass, or
     prompting as an option.  The system administrator must
     know what types of modems are being used by remote
     users and set the Dial Security parameters accordingly.
     Autopass is limited to U.S. Robotics modems with Dial
     Security, and prompting is not.

Register S53 is used to enable Dial Security, and is a bit-
mapped register.  Select the Dial Security options you want



and set S53 according to the table below.

          Bit  Result
          -----------------------------------------------
          0    Dial security enabled.
          1    Prompting enabled when bit 0 is on.
          2    Local-access password protection enabled
               when bit 0 is on.

          Table C.1-Dial Security Functions for Host

The &W command must be used to save Register S53 settings to
NVRAM.  Otherwise, when the computer is powered off and on
again, or the modem is reset using ATZ, it will default to
S53=0, Dial Security disabled.

To enable autopass with local access password protection,
but without prompting, type the following command.
          AT S53.0=1 .2=1 &W <Enter>

The following command enables Dial Security with prompting,
and local access password protection.
          AT S53.0=1 .1=1 .2=1 &W <Enter>

6.   Check to see that DIP switch 10 is OFF (factory
     setting) so that the modem loads the settings stored in
     NVRAM, as well as Dial Security information.
     WARNING:  If someone sets DIP switch 10 ON, the factory
     read-only (ROM) defaults are loaded, and Dial Security
     is disabled.  If this should happen, reset DIP switch
     10 to OFF, power off the computer and power it back on,
     or reset the modem by typing ATZ <Enter> so that the
     proper setting takes effect.

LOGIN OPERATIONS
------------------------------------------------------------

Autopass
--------
Autopass is only possible between two U.S. Robotics modems
with Dial Security.

When autopass is enabled, the remote modem must send a valid
autopass password in order to connect.

If a remote user has set up the modem with an invalid
password, or has failed to enable Dial Security, the host
modem returns an Invalid Password message and hangs up.

Prompting
---------
When prompting is enabled, a remote caller must match one of
the account passwords to connect.
If the remote modem doesn't have error control capabilities,
the host modem will still allow a connection, provided the
host is set to &M4 so it can also answer non-error
correcting calls.

If the modems are compatible, the host modem prompts the
caller for a password, and waits 60 seconds before
disconnecting.  The host modem checks the received password
against each of its active Dial Security accounts.  If the
password is invalid, the host modem prompts twice more
before disconnecting.

Optional Dialback
-----------------
When the host modem receives a valid password, and an
account's dialback field is enabled, the host disconnects.
The remote user receives a NO CARRIER message.  Then the
host modem dials back the remote modem, typically at the
number stored in the phone number field.  The dialback
process takes approximately one minute due to telephone
company requirements.

However, if the account allows a new number, the host
prompts the remote user for the new number before hanging
up, and then dials back.

ACCOUNT MAINTENANCE
------------------------------------------------------------

Once the local access password is set and protected, the
system administrator is the only one who can access account
information.  To modify or change account information, use
the %S= and %E= commands described next.

Account Access (%S)
-------------------
The system administrator can access accounts one of two ways
once Dial Security is enabled:
#    disable Dial Security and edit the accounts using the
     %An= command.
#    enter your local access password using the %S= command,
     which allows access to the accounts without disabling
     security.
          AT%S=(your local access password) <Enter>

NOTE:  The modem echoes the local access password, which is
case sensitive.  If the password is Bob and is entered as
BOB, for example, an OK is displayed.  However, if you try
to type another command, for example,  ATI10 <Enter> to view
accounts, an Access Denied message is displayed.  Be sure to
enter the password in the exact way as it was set up.

Once access has been granted you can view and/or edit
account information using the following commands.

Account Status
--------------
To view account information, type the following command.
          ATI10 <Enter>

This command is only valid for remote users if local access
security is disabled.

Erasing Account Information (%E)
--------------------------------
Use the %E= is command to make system edits.
%E=1 Erases local access password.
%E=2 Erases autopass password.
%E=3 Erases passwords in accounts 0-9.
%E=4 Erases phone numbers in accounts 0-9.
%E=5 Disables Account, Dialback and New Number
     fields in accounts 0-9 disabled.

To edit or overwrite an individual account, or an individual
account field, use the %An= command described in Setting Up
Accounts, earlier in this appendix.

Remote Configuration
--------------------
To remotely configure Dial Security accounts, see
Configuring Dial Security Remotely at the end of this
appendix.

DIALING IN
------------------------------------------------------------

Remote users must perform the following operations in order
to call into the host's Dial Security system.

1.   For prompting, get a password from the system
     administrator.  For autopass, get a password or account
     number (0-9) from the system administrator.  Passwords
     are case-sensitive, so be sure to copy it down
     correctly.  For prompting, skip to step 3 if the
     administrator enables dialback for your account.

2.   For autopass only.  Set up the remote modem to send the
     autopass password during the connection sequence, using
     the %V= command as in the following example.
          AT %V=Ryan <Enter>

Alternatively, just use your the account number as the
autopass password, as in the following example.
          AT %V=PW9 <Enter>

NOTE:  It doesn't matter if the autopass password is the
same as the system administrator's local access password.

You can check to see that you've correctly set up your
autopass password by typing the following command.  Your
autopass password appears in the righthand column below
FORCED AUTOPASS.
          AT I10 <Enter>

Once the autopass password is set, Dial Security must be
enabled with the following command.
          ATS53.0=1 &W <Enter>

3.   Set the modem to automatically answer incoming calls--  
     only if dialback is enabled.

If the host modem qualifies an autopass password, and
dialback is enabled, the host disconnects the incoming call
and dials back the remote caller.  This process usually
takes about one minute due to telephone company
requirements.

The Courier is shipped with DIP switch 5 ON, Auto Answer
suppressed.  To set the modem to automatically answer
incoming calls, set DIP switch 5 OFF and reset the modem
(ATZ <Enter>).

Or set the modem to answer on the first ring by typing the
following command, and save it to NVRAM with the &W command.
          AT S0=1 &W <Enter>


------------------------------------------------------------
REMOTE ACCESS OPERATIONS
------------------------------------------------------------

You can set a Courier modem so that it can be remotely
configured by someone at another modem.  This is especially
helpful when you have problems making a connection with
another modem.  For example, if you have trouble connecting
with a bulletin board, you can allow the bulletin board
operator to dial in to your modem and view its configuration
settings.  If necessary, the bulletin board operator can
send the Courier a configuration string to correct your
settings.  Another use might be for Dial Security
administration when the system administrator is unable to be
at the host modem site.  It might be urgent, for example, to
disable an account.

AT THE COURIER SITE
-------------------

Setting the Courier for Remote Access
--------------------------------------
There are two tasks required to use remote access:
#    set up password security
#    enable remote access

Password Security
-----------------
You can designate two passwords for remote access security,
each allowing a different level of access to the remote
user.  You can assign one password that allows viewing
privileges only, whereby the Courier's configuration can be
remotely viewed but not changed.  You can assign another
password that allows both remote viewing and configuration
privileges.

Passwords can be up to eight alphanumeric characters long,
and are not case-sensitive.  To assign a password that
allows viewing privileges only, use the following command
format.
          AT%P0=[password] <Enter>

To assign a password that allows viewing and configuration
privileges, use this command format.
          AT%P1=[password] <Enter>

NOTE:  If you enable remote access by pressing the
voice/data switch while powering on the modem, previously
set passwords will be erased.

LED Indicator for Remote Access
-------------------------------
The Courier's SYN LED flashes to indicate when it is in a
remote access session.

Enabling Remote Access
----------------------
There are two ways to set the Courier modem for remote
access.
#    Set Register S41 for a value of 1 or greater.  S41 is
     used to set the number of allowable login attempts, as
     explained later.  A setting of zero allows no login
     attempts, and thus disables remote access.

#    Press and hold down the voice/data switch while pow
     ering on the modem.  Pressing the switch during power-
     on causes the modem to perform its normal self-test,
     enables Auto Answer, enables Remote Access by changing
     the S41 setting to 1, and disables password security.

Disabling Password Security
---------------------------
If you want to disable an assigned password (and thereby
disable remote access security), use the following command
format.
          AT%P0= <Enter>
          or
          AT%P1= <Enter>

If, for example, you disable the %P0 password, a remote user
does not need to enter a password for view-only access.

AT THE REMOTE MODEM SITE
------------------------------------------------------------

Remote configuration can be performed at any time during an
asynchronous connection.  The user performing remote
configuration can use any modem; it does not have to be a
U.S. Robotics model.

1.   Make sure the Courier has been set for remote
     configuration, as described earlier, and establish a
     connection.  It does not matter which modem originates
     the call.

2.   After a connection has been established, send the
     following escape sequence.
     Pause four seconds,
     type four tildes: ~~~~
     and
     pause another four seconds.

     NOTE:  You can change the escape sequence character
     with Register S42.  The pause duration (guard time) can
     be modified with Register S43.  (These values are set
     at the Courier modem.)

3.   When the Courier begins its login sequence, the caller
     will see a display similar to the following.

     U.S Robotics Courier HST Dual Standard terbo Fax Remote
     Session
     Serial Number 000000A000000001

4.   At this point, if password security is active, the
     caller is prompted for the password.
     Password (Ctrl-C to cancel)?.....
     
     As described earlier in Password Security, entering the
     password assigned with %P0 allows viewing privileges
     only.  Entering the password assigned with %P1 allows
     viewing and configuration privileges.  Note that there
     is a 3-minute time limit for entering the password.
     
     As mentioned earlier, if the number of unsuccessful
     login attempts exceeds the set limit, the modem returns
     online and refuses any further login attempts during
     the remainder of that connection.
     
     When a password is accepted, the Courier indicates that
     it has entered Remote Access mode and the remote prompt
     appears on the caller's screen.
          Access Granted
          Remote->

5.   If password security is not active (no passwords have
     been set or both passwords are disabled), the Courier
     automatically enters Remote Access mode and the remote
     prompt appears on the caller's screen.
          Remote->

6.   Once the remote access session has been established,
     keep in mind that there is a 3 minute inactivity timer.
     If the modem detects no activity for 3 minutes, it
     aborts the remote access session and resumes a normal
     online connection.

Aborting the Request for Remote Access
--------------------------------------
You can abort the remote access login procedure and return
online by pressing the key combination <Ctrl>-C.

Remote Viewing and Configuration
--------------------------------
Once you've gained remote access, you can communicate with
the Courier as if you were typing commands at its attached
computer.  Depending on your access privileges, you can use
the regular Courier AT commands.

If you have view privileges only (with Password 0), you can
use any of the view commands described in Chapter 5.

If you have view and configure privileges (set with %P1),
you can use any of the modem commands, except those commands
that cannot be used while online, such as the Dial command.
You can also use the remote access commands explained later.

When you make remote configuration changes, the remote
prompt is altered to indicate that changes have been made.
The prompt will change from:
     Remote->
          to
     Remote+>

If you restore the original configuration (with %C1,
explained next), the original prompt is also restored (back
to Remote->), indicating that the original configuration is
intact.

By default, configuration changes do not take effect until
the connection is terminated (see %Cn).  However, the new
configuration is immediately reflected in the information
screens (ATIn).





REMOTE CONFIGURATION COMMANDS
------------------------------------------------------------

There are some additional commands that are only executable
during a remote access session.  These commands are as
follows.

%Bn  Configure the Courier's serial port rate.
     %B0  110 bps.       %B6  9600 bps.
     %B1  300 bps.       %B7  19,200 bps.
     %B2  600 bps.       %B8  38,400 bps.
     %B3  1200 bps.      %B9  57,600 bps.
     %B4  2400 bps.      %B10 115,200 bps.
     %B5  4800 bps.

%Cn  Configuration control.
     %C0  Defer configuration.   This is the default.
          Configuration changes are deferred until the call
          is ended, and take effect for ensuing connections.
          You do not need to enter this command; it is the
          default unless you enter one of the following %C
          values.

     %C1  Restore configuration.  Use this command to cancel
          any configuration changes made during remote
          access, and restore the original configuration.   
          However, commands that have been written to NVRAM
          (with &W) will not be restored to their previous
          settings.  Additionally, if you have forced
          immediate configuration changes (with %C2), those
          changes cannot be reversed with %C1.

     %C2  Execute configuration.  Use this command to force
          configuration changes to take effect immediately,
          during the current connection.  We recommend      
          against forcing immediate configuration changes   
          unless absolutely necessary, as this can result in
          an unreliable connection or even a loss of
          connection.

%Fn  Configure data format.

     %F0  No parity, 8 data bits.

     %F1  Mark parity, 7 data bits.

     %F2  Odd parity, 7 data bits.

     %F3  Even parity, 7 data bits.





Password Commands
-----------------
%Pn=      Disables password security (n=0 or 1) when no
          character follows the equal sign.

%Pn=s     Specify the following password string (s) for
          viewing privileges only (n = 0) or view and
          configuration privileges (n= 1).

%Pn?      Display password n.

Command Format
--------------
When typing commands during the remote access session, no
delay between command strings is necessary.  For example,
you can type the following commands without pausing after
each one.

#    a password:  ABCDEF <Enter>
#    a configuration string: AT&H1&R2&W <Enter>
#    and a request for an information screen: ATI5 <Enter>

The maximum number of characters between carriage returns is
40.

ENDING A REMOTE ACCESS SESSION
------------------------------------------------------------

One of three commands ends a remote access session.

#    ATZ resets the modem and terminates the connection.
#    ATH terminates the connection.
#    ATO ends the remote access session, but the modems
     remain online.

CONFIGURING DIAL SECURITY REMOTELY
------------------------------------------------------------

The system administrator can configure account information
from a remote site, using the following procedures.

NOTE:  Before remote configuration is possible, the local
modem's remote access must be enabled, and a remote access
password that allows viewing and configuration privileges
must be assigned.  For convenience, you may want to use your
local access password as your remote access password.

Dialing In From the Remote Site
-------------------------------
1.   From the remote site, connect to the host modem using
     Dial Security.  Once a connection is made, follow the
     instructions for beginning a remote access session as
     described later in this appendix.
2.   When remote access has been granted, use the %S=
     command to access the Dial Security accounts.

3.   If you wish, you can view account information by typing
     the following Inquiry (I) command.
          AT I10 <Enter>

4.   Make any configuration changes and save them
     immediately by typing the following command.
          AT %C2 <Enter>

5.   To end the remote session and reactivate local access
     security on the host modem, reset the modem by typing:
          ATZ <Enter>

     WARNING:  If you do not use the ATZ command to end a
     remote access session, Dial Security will remain
     disabled and anyone dialing in to the local modem will
     have access to all Dial Security accounts.




































+----------------------------------------------------------+
|                                                          |
|   APPENDIX D.  TROUBLESHOOTING                           |
|                                                          |
+----------------------------------------------------------+

You may occasionally encounter one of the problems listed
here.  They are divided into two categories:  before and
during the exchange of user information over the data link.

BEFORE ESTABLISHMENT OF THE DATA LINK             
------------------------------------------------------------


Your modem doesn't answer the phone or go off hook to dial a
number
------------------------------------------------------------

Review the quick configuration guide (labeled STOP) that
came with the modem or your communications software manual
to see what Data Terminal Ready (DTR) operations your
software requires.  Then check to see if DIP switch 1 is set
correctly.  Also, check to make sure your terminal or
computer is sending a DTR signal via the RS-232 interface.


Your modem doesn't respond OK when you type AT <Enter>
------------------------------------------------------

1.   Make sure you're typing in either upper case or lower
     case letters, not a combination, and that you press the
     Enter key.

2.   If you're using a computer, make sure it is in Terminal
     mode.  This is a communications software function.  See
     Testing the Modem in Chapter 2.

3.   Check to see that your terminal or software is set to  
     the correct bit rate and word length (7 bits with or
     without a parity bit, or 8 bits and no parity).  If
     you're using a computer, make sure your software is set
     to the correct communications port.

4.   Check that DIP switch 8 is ON, for command set
     recognition.  If the switch is OFF, power off the
     modem, set the switch ON, and power on the modem again.
     Try typing AT <Enter> again.

5.   Check that DIP switch 3 is ON, for result code display,
     and that DIP switch 2 is OFF, for verbal result codes.
     If not, change the switch(es) and type ATZ <Enter>.  Or



     type whichever of these commands is needed:

          ATQ0 <Enter>   (to enable the message)
          ATV1 <Enter>   (to display a verbal message)

6.   Review the STOP guide that came with the modem or your
     communications software manual to see what Carrier
     Detect (CD) operations your software requires.  Then
     check to see if DIP switch 6 is set correctly.

7.   A rare condition is that your terminal or computer
     reverses the send/receive functions at the RS-232
     interface.  See the description for Quad switch in
     Appendix B, and your equipment documentation.


Your modem displays double characters
-------------------------------------
Both your modem's and software's local echo are on.  You can
turn your software's local echo off.  Or turn the modem's
echo off by either resetting DIP switch 4 and sending the
modem the ATZ command, or by sending the modem the ATE0
command.


Your computer reacts as though a data link has been
established, but no call has been received
----------------------------------------------------------

DIP switch 6 is set ON at the factory for Carrier Detect
(CD) override, but your system may require that the override
be turned OFF.

Review your terminal's manual, the STOP guide that came with
the modem or your communications software manual to see what
CD operations are required.  Then check to see if DIP switch
6 is set correctly.


When the modem is in Answer mode, it acts as though a
Carriage Return has been entered, but nothing has been typed
at the keyboard
------------------------------------------------------------

Your software may be misreading signals from the modem as it
automatically sends a Carriage Return and a Line Feed before
and after the RING and CONNECT messages.  Sending the Quiet
mode command, ATQ1 <Enter>, should solve the problem.






Both modems exchange carrier signals, but fail to establish
a communications link
------------------------------------------------------------

1.   If you have a fax modem, make sure it is in the correct
     mode, fax or data, depending on whether the connection
     is to be made with a facsimile device or a data modem.
     See Fax Operations in Chapter 4 for information on
     switching between Fax and Data modes.

2.   Asynchronous operations:  Check to make sure the proper
     bit rate, word length, parity and number of Stop bits
     have been selected.  Synchronous operations:  review   
     the link instructions in Appendix E. If you've set the
     modem to the correct configuration, the problem may be
     with the synchronous adapter or with the system you're
     trying to call.

3.   Check to see that your modem is at the correct Bn
     setting to connect with either an HST modem (B1
     setting) or V.32 terbo modem (B0 setting).  Type ATI4
     for a display of the Courier's current settings and, if
     necessary, send the modem the correct setting.

4.   If your modem is attempting to answer a V.32 call, you
     may need to lengthen the extra V.32 answer tones.  See
     S28 in Appendix B.

5.   Depending on your model, make sure the modem at the
     other end of the line is HST compatible, V.32 terbo
     compatible at 14.4K bps, or V.32 compatible at 9600
     bps, V.22 bis-compatible at 2400 bps, Bell 212A-
     compatible at 1200 bps, or Bell 103-compatible at 300
     bps.  These are the common signaling standards for full
     duplex dial-up network transmission in the U.S.

6.   Make sure your modem's connection rate setting, &Nn is
     correct for the call.  If the connection rate is locked
     at a speed (&N1+&N10) different from the calling
     modem's, the Courier hangs up.  The factory setting of
     &N0, variable link operations, allows the two modems to
     negotiate the highest possible connection rate.

7.   If none of the above corrects the problem, it's likely
     that the quality of the phone connection is poor and
     that the other modem is missing the signals your modem
     is transmitting.  The variable quality of phone line
     connections may be due to any number of conditions in
     the phone service's equipment or the current
     environment.  Try several calls, and if you still can't
     get through, try calling another modem.  If the second
     modem accepts your call, the problem may lie with the
     modem you first tried to call.

During Data Transfer Your Screen Displays Only Brackets
-------------------------------------------------------

Check to make sure that both modems are set to the same bit
rate, word length, parity and number of Stop bits.  If the
settings are correct, the problem may be with the phone
line.  Try the following measures:

1.   Try placing the call again.  The phone company routes
     even local calls differently each time you call.

2.   Try calling a different modem to see if the problem
     persists.  The problem may be with the modem you first
     tried to call.

During Data Transfer Your Random or Garbage Characters
-------------------------------------------------------

Check to make sure that both modems are set to the same bit
rate, word length, parity, and number of Stop bits.

If the modem is set to a fixed serial port rate (&B1) and
your software is fixed at 19.2K, 38.4K, 57.6K, or 115.2K
bps, the reason may be one of the following:

1.   Your computer may not support the high rate.  If this
     is the case, fix your software rate at 9600 bps and
     disable high-speed V.32 terbo modulation: ATS34=3 or   
     ATS34 .0=1 .1=1.

2.   If you use memory-resident programs (TSRs), they may be
     interfering.  Try disabling them before you run your
     communications software.  The same is true of disk-
     caching programs.

3.   Check to see that your software and the modem are set
     for the same kind of flow control, either hardware or
     software.  Some communications programs also require
     that you disable the kind you are not using.

During File Transfer Your Screen Displays Double Characters
------------------------------------------------------------

Your modem's online local echo is on and the remote modem is
also echoing.  The only way to correct this is to bring the
modem back to Command mode (wait one second without
transmitting data, type +++, wait another second).  Then
type the command to turn off your online echo (ATF1
<Enter>).

If DIP switch 9 is OFF (factory setting), the modem hangs up
when it returns to Command mode, and you'll have to call
again.  If DIP switch 9 is ON, the modem maintains its

connection.  You can return it back online by typing ATO
<Enter>.

IF YOU STILL HAVE PROBLEMS    
------------------------------------------------------------

The problems described above are by far the most common ones
that users encounter.  If the suggestions we've given don't
clear up your difficulties, try the following:

1.   Review the manual carefully to see if you've missed
     something.

2.   Call or visit your dealer.  Chances are your dealer
     will be able to give you the assistance you need.  This
     is much more efficient and time-saving than returning
     the modem to U.S. Robotics.

3.   If your dealer can't clear up your difficulties, call
     the U.S. Robotics Technical Support Department at 800- 
     982-5151, or send a fax to 708-982-0823.  Our Service
     Representatives will be happy to give you assistance
     over the phone Monday through Friday from 8:00 a.m. to
     6:00 p.m. (Central Time Zone).

4.   If necessary, the Service Representative you talk to
     may give you a Return Materials Authorization (RMA)
     number.  Modems without an RMA number will not be
     accepted.

5.   If you do return the modem to us, please use the
     following procedures.

     a.   Ship the unit, postage paid, in its original
          container.  If the original container is not
          available, pack the modem carefully in a strong
          box of corrugated cardboard with plenty of packing
          material.

     b.   Be sure to include your RMA number inside the
          package, along with your name and address.  Put
          your return address and your RMA number on the
          shipping label as well.











     c.   Ship the well-packed modem to the following
          address.

          Technical Support Department
          U.S. Robotics, Inc.
          8100 North McCormick Boulevard
          Skokie, Illinois 60076-2999

     d.   Please note that U.S. Robotics will not accept
          packages sent COD, so be sure to send the modem
          postage paid.

     e.   U.S. Robotics will repair your modem and return it
          to you via United Parcel Service.








































+----------------------------------------------------------+
|                                                          |
|   APPENDIX E.  SYNCHRONOUS AND                           |
|   DEDICATED AND LEASED LINE OPERATIONS                   |
|                                                          |
+----------------------------------------------------------+

SYNCHRONOUS APPLICATIONS
------------------------------------------------------------

Synchronous mode is required for users who need to call, or
receive calls, from a Host computer of a large network.  The
Host is usually a mainframe.  There are two ways the Courier
can operate in synchronous mode:

#    Selecting the ITU-T standard V.25 bis protocol, which
     formats data in HDLC or character-oriented frames.
     This method is used by mainframe operators and
     synchronous terminal users.

     V.25 bis acts as an interface between the mainframe and
     modem, sending synchronous responses between the modem
     and the mainframe.  An asynchronous device or a "dumb"
     terminal is used to configure the modem before it dials
     out in synchronous mode.

#    Dedicating a PC as a synchronous device by installing  
     the proper hardware and software so it can communicate
     with a mainframe.  The modem is configured and dials
     out in asynchronous mode, then switches to synchronous
     mode once a connection is made.

     NOTE:  HST modulation is not supported for synchronous
     communications.

GENERAL REQUIREMENTS
------------------------------------------------------------

Courier modems in asynchronous mode adapt to many conditions
of remote asynchronous modems.  But synchronous connections
to a mainframe require strict adherence to specific
operating parameters.  If you are operating a terminal
designed for a particular network, you probably need only
set the Courier properly before calling or answering.

NOTE:  The term DTE in the following discussion means Data
Terminal Equipment, the end-to-end equipment involved in
data communications.  DTE denotes your terminal or computer
and the remote computer.






What You Need to Know
---------------------
The network's communications management staff can supply
information on the following requirements:

#    The protocol needed for your calls

#    The software support needed to log into the network,
     for example, a specific communications package or
     interface board

#    The phone number, if you will be calling instead of
     answering
#    Any restrictions about when you can call

The RS-232 Interface
--------------------
Transmit and Receive synchronous timing pins are required at
the RS-232 interface.  You'll need either pin 15 or pin 24
for Transmitter timing signals, depending on whether the
modem (pin 15) or the DTE (pin 24) generates the signals.
You'll also need pin 17, for Receiver timing signals.  If
you're building your own cable, review the RS-232 Interface,
in Appendix B.

Protocol Compatibility
----------------------
The devices at both ends of the link must use the same
protocol.  These protocols format data into blocks or frames
and add control information.

If the modem is in V.25 bis mode, the link protocol must be
HDLC (High-Level Data Link Control), or character-oriented.
If the modem is in Online Synchronous mode it may use HDLC,
character-oriented, or another protocol determined by the
mainframe manufacturer.

Data Rate Synchronization (&Xn)
-------------------------------
During synchronous operations, transmit and receive clocks
at both ends of the phone link control the precise timing of
the data flow.  The communications equipment at the remote
DTE and your modem and DTE must all handle the data at the
same speed.

The transmit clock timing signals setting, &Xn, determines
whether the modem or DTE will generate the timing signals.
For Online synchronous operations, the source for this
setting must be the same on both systems.  For V.25 bis
operations this is not necessary.  See Connection Rates
(%Nn, &Nn later in this appendix).



Most Online synchronous users will require the default
setting, &X0.

&X0  The Courier is the source of the Transmit clock timing
     signals and sends them to your DTE over the RS-232
     interface.  The DTE rate will follow the connection
     rates.  Default.

&X1  The DTE is the source of the Transmit clock timing
     signals and sends them to the Courier over the RS-232
     interface.  This setting is used typically in leased
     line multiplexed operations.  (Multiplexors divide the
     phone channel so that the channel carries several calls
     at the same time.)
     
     The DTE ignores the Courier's clock timing signals and
     negotiates the DTE and connection rates.

&X2  The Courier's Receiver clock is the source of the
     timing signals.  The signals are looped to the Transmit
     clock and sent to your DTE over the RS-232 interface.
     This setting is only used in those systems that require
     synchronization of data flowing in both directions.

V.25 BIS REQUIREMENTS
------------------------------------------------------------

V.25 bis is a ITU-T standard that uses the HDLC or
character-oriented protocols to format data.

Before you attempt to connect to a synchronous network, you
must configure the modem in command (asynchronous) mode by
using either an asynchronous device or dumb terminal.  Once
the modem is in synchronous mode, it no longer accepts
asynchronous commands.

To set the modem, follow the instructions in Chapter 3,
Command Set Usage.  Commands begin with a required AT prefix
and end with a required Carriage Return, which we denote
with the symbol <Enter>.  For example, the following command
causes the modem to set the connection rates, enable normal
result codes, enable auto answer, select HDLC as a link
protocol, and save the settings to NVRAM.  Spaces have been
added only for readability.
          AT &N0 %N6 X0 S0=1 &M7 &W <Enter>

Be sure that DIP switch 10 is OFF so that the modem loads
the settings you've stored in nonvolatile random access
memory (NVRAM) when it powers on.  Until you customize your
own settings, the settings in NVRAM are the same as the
factory defaults.



Connection Rate (&Nn, %Nn)
--------------------------
The &Nn and %Nn commands work in conjunction with &Xn.  If
the modem is set so that it is the source of the Transmit
clock timing signals (&X0-default) the %Nn commands set the
computer or terminal-to-modem V.25 bis clock speed.  If the
modem is set to &X1, the computer is the source of the
Transmit clock signals, but it still follows the rate set by
the %Nn command.  In both cases, the &Nn command sets the
online connection rate.

Sample Settings
---------------
In originate mode, if the modem is set to &X0, &N0 and %N6,
it will establish the highest possible connection rate
(&N0), but will be limited to 9600 bps because the %N6
command sets the modem's clock speed at 9600 bps.

In answer mode, if the modem is set to &X0, &N0 and %N7, for
example, it tries to connect at the highest possible speed
negotiated by the two modems.  If, however, the modem is set
for a specific value like &N7 (12200 bps) instead of &N0,
the modem ignores the %Nn command and tries to connect at
that &Nn speed.  If it doesn't connect, it hangs up.

Unlike the &Nn command, setting a specific rate with the %Nn
command doesn't fix the connection rate.  If the modem is
set for &X0, &N0 and %N6, for example, and doesn't make a
connection at 9600, it will drop down to the next available
speed of the remote modem.  The modem negotiates the highest
possible connection rate, depending on the remote modem's
capabilities.

To avoid confusion, we recommend that the modem be set with
a fixed rate between the computer or terminal and modem
(%Nn) and that the connection rate (&Nn) be set to the same
rate.

The &Nn rates are as follows:
&N0     Variable (default)    &N6  9600 bps
&N1     Reserved              &N7  12K bps
&N2     1200 bps              &N8  14.4K bps
&N3     2400 bps              &N9  16.8K bps      
&N4     4800 bps                   (terbo+to+terbo only)
&N5     7200 bps              &N10 19.2K bps (terbo+to+terbo
                                   only)

If &Nn is set for 2+10, the modem ignores the %Nn rate and
follows the &Nn rate to set the Online connection rate.





If %Nn is set to 0 or 1, you will receive an error message
since they are not valid values.  The %Nn rates are as
follows:
%N0     Reserved         %N6  9600 bps (default)
%N1     Reserved         %N7  12.2K bps
%N2     1200 bps         %N8  14.4K bps
%N3     2400 bps         %N9  16.8K bps
%N4     4800 bps         %N10 19.2K bps
%N5     7200 bps

Result Codes (Xn)
-----------------
The Courier displays normal or extended synchronous result
codes, depending on the setting of the Xn command.  By
default, the modem is set to X1 for extended result codes.
To change to normal result codes, set the modem to X0.

The normal result codes return messages such as VAL or INV
(VALID or INVALID), whereas the extended codes offer
explanations--INVPS (INVALID Parameter Syntax Error).

Automatic Answering (S0=1)
--------------------------
When the Courier is operating in V.25 bis mode, it ignores
the DIP switch 5 setting, which controls Auto Answer.  To
set the modem to automatically answer incoming calls, set
the modem to S0=1, so it answers on the first ring.  You can
substitute a higher value.  See the S-Register summary in
Appendix B.

Suppressing Auto Answer
-----------------------
To disable Auto Answer, set the modem to answer on zero
rings, S0=0.

Choosing a Synchronous Protocol (&Mn)
-------------------------------------
Once the &Xn, %Nn, &Nn, Xn, S0 commands are configured, you
must use the &Mn command to choose the HDLC or character-
oriented link protocol so that your synchronous software can
properly format its commands.

&M6  Use the character-oriented protocol for synchronous
     communications.

     The Courier and the remote modem must use the same
     eight-bit data format.  The character length must be 7
     bits and either ODD or EVEN parity (ODD is preferred),
     or 8 bits and NO parity.

&M7  Use the High Level Data Link Control (HDLC), a ITU-T
     standard, for synchronous communications.  HDLC ignores
     parity.

V.25 bis Commands and Result Codes
----------------------------------
Supported V.25 bis commands and result codes are listed in
Appendix I.

Hanging Up
----------
Since the modem cannot accept commands once it is connected
in synchronous mode, you cannot use the ATH (hang up)
command or the +++ escape sequence.
The only way for the modem to disconnect is to drop its DTR
signal.  This is normally done with software.  However, if
the modem is initially set to S32=6 when it is in
asynchronous mode, the modem will reset when the voice/data
switch is pressed, thus dropping DTR.

Returning to Asynchronous Mode
------------------------------
Once you've completed a communication session, you can
switch between synchronous and asynchronous modes by
flipping DIP switch 10 OFF (factory settings, asynchronous
mode) and then ON (NVRAM settings, synchronous mode if the
modem is set to &M6 or &M7).

The modem cannot switch between synchronous and asynchronous
while it is connected.

ONLINE SYNCHRONOUS REQUIREMENTS
------------------------------------------------------------
Although personal computers do not usually support
synchronous communications, they can be dedicated to do so.
If you have a personal computer you must find out what
hardware and software you need before setting the Courier
for synchronous calls.

The Synchronous Adapter Card
----------------------------
You will probably have to purchase and install a synchronous
adapter card.  These cards are multifunction boards that
provide the following functions:

#    A synchronous port from the DTE to the modem.

#    One or more synchronous protocols.  Be sure to find out
     which protocol the Host mainframe requires before you
     purchase an adapter.

#    Additional software functions.  For example, you need
     to identify the type of computer or terminal you are
     using to the mainframe software.  You will most likely
     also have to specify your application, that is,
     identify the mainframe resources you want to use.


Setting the Modem
-----------------
When the modem is set to Online Synchronous mode, it remains
in command (asynchronous) mode until it makes a synchronous
connection with a remote modem.  Upon connection, the
Courier enters synchronous mode and sends synchronous timing
signals to your DTE.

Because the modem will not accept commands when it is in
synchronous mode, you will have to configure it in
asynchronous mode before trying to connect to a synchronous
network.

NOTE:  Be sure that DIP switch 1 is OFF (factory setting).
The Data Terminal Ready (DTR) override must be OFF so that
the Courier detects when the DTE raises and lowers the DTR
signal.

To set the modem, follow the instructions for issuing
commands in Chapter 3, Command Set Usage.  Commands begin
with a required AT prefix and end with a required Carriage
Return, which we denote with the symbol <Enter>.

For example, the following command causes the modem to set
the modulation, the connection rate, and choose a timing
source.  Spaces have been added only for readability.
          AT B0 &N0 &X0 <Enter>

Modulation/Connection rate (Bn, &Nn)
------------------------------------
Use the following guidelines for your Courier type.

V.32 terbo modems:  If the modem is connecting with another
U.S. Robotics V.32 terbo modem, set both modems to B0 and to
a variable connection rate, &N0.  The modems will connect at
the highest possible rate.

If the Courier V.32 terbo is to connect with a V.32 modem,
set the Courier to B0 and try a variable connection rate
first, &N0.  If that doesn't work, try a fixed connection
rate of &N6 (9600 bps) or &N3 (2400 bps).

Modems in HST mode:  HST modulation for synchronous
communications is not supported.

Dual Standard modems:  Set the Dual Standard modem to B0.
Try a variable connection rate setting (&N0) first.  If that
doesn't work, you may have to set a fixed connection rate,
for example, &N6 (9600 bps).

NOTE:  If your modem is set to a fixed rate, and the remote
modem is not set to the same rate, your modem hangs up.


Connection Rate (&Nn)
--------------------
Use this command to set variable or fixed rates at the link
interface.  The default is &N0, variable rate.  The Courier
negotiates with the remote modem for the highest possible
connection rate, depending on the capabilities of the remote
modem.  If &N0 does not work, try a fixed rate.

NOTE:  The modem is not capable of connecting at 21.6K bps
in synchronous mode.


When you set the modem to a fixed rate it will only connect
if the remote modem is operating at the same rate.  If not,
your modem hangs up.

The fixed rate options are as follows.

&N0    Variable rate     &N6  9600 bps
&N1    Reserved          &N7  12K bps
&N2    1200 bps          &N8  14.4K bps
&N3    2400 bps          &N9  16.8K bps
&N4    4800 bps               (terbo+to+terbo only)
&N5    7200 bps          &N10 19.2K bps (terbo+to+terbo
                              only)

Generating Clock Timing Signals
-------------------------------
The &Xn setting specifies whether the Courier or your DTE
generates the Transmit clock timing signals for a
synchronous call.  Most users will require the default
setting, &X0.  See Data Rate Synchronization (&Xn), earlier
in this appendix, for more information.

Dialing Out
-----------
The modem's stored command feature (&ZC=s) allows you to
configure the modem for a synchronous connection and to dial
out to the Host computer by just pressing the voice/data
switch.  Below are our recommended procedures.

1.   If your communications software isn't running, load the
     program and put the computer in Terminal mode, as
     described in the Chapter 2.  Terminal mode allows you  
     to send AT commands directly to the modem.

2.   Store a command string (&ZC=s) that configures the
     modem according to the guidelines in Chapter 3, and the
     Host computer's requirements.  In addition, include the
     &M1 command, to have the modem enter synchronous mode,
     followed by the appropriate Dial string.  The following
     is an example:
          AT &ZC = &F &X1 &M1 DT5551234 <Enter>

     In the example, &F restores the modem's factory
     defaults, while &X1, which specifies the computer as
     the synchronous timing source, is the only non-default
     setting used besides synchronous mode (&M1).  Any non-
     default settings should follow the &F command.  The
     Dial command should be the last entry before the
     Carriage Return.

3.   Set the voice/data switch to option 9, so that the
     modem executes the stored command string when you press
     the switch.  Type the following:
          ATS32 = 9 <Enter>

     NOTE:  If you usually use the voice/data switch for
     another purpose, you can include the execute stored
     command option S32 = 9 in the stored command string.
     However, the total number of characters may not exceed
     30.

     If S32=9 is used with the stored command string it
     over-writes any other S32 option.  Once the
     communication session is over, you will have to reset
     S32 if you want to select another option.

4.   Press the voice/data switch when you want to connect
     with the synchronous Host computer.  You need not have
     your communications software loaded at the time.

5.   After the call, restore the modem to asynchronous oper-
     ations by powering it off and on again.

Answering
----------
To configure the modem for Answer mode using the voice/data
switch, follow the instructions in the previous section,
Dialing Out, but with these modifications:

#    Insert S0 = 1 in the stored command, Step 2.  This sets
     the modem to Auto Answer.

#    Omit the Dial string shown in the same step (DT and    
     phone number).

If you don't wish to use a stored command and the voice/data
switch, send the modem the appropriate configuration string,
ending with &M1.  The following command adapts the dial-out
command example.  Note again that all non-default settings
follow the &F command.
          AT &F S0=1 &X1 &M1 <Enter>

The modem responds automatically to an incoming call, enters
synchronous mode and, in this case, because it is set to
&X1, waits for synchronous timing signals from your DTE.

Hanging Up
----------
The modem remains online until the remote modem disconnects
or your software causes the DTE to drop the Data Terminal
Ready signal (DTR).  The Courier sends the NO CARRIER result
code if result codes are enabled, and returns to
asynchronous Command mode.

Testing and Inquiry Commands
----------------------------
The modem testing commands, &Tn, and inquiry commands, In,
cannot be used when the modem is operating in synchronous
mode.

------------------------------------------------------------
     DEDICATED AND LEASED LINE OPERATIONS
------------------------------------------------------------

The following operations apply in installations where the
modem's phone line is not part of a public-access switched
telephone network.  Instead, the modem is connected to a
special user-installed telephone line or a line that is
leased from the telephone company.  These lines are often
referred to as dedicated (to a pair of modems) or private
lines.

In both types of installation there is a continuous point-
to-point connection between two modems.  No dialing of phone
numbers is required.  The modems may be in either Smart or
Dumb mode (determined by the position of DIP switch 8).

The User-Installed or Leased Telephone Line
-------------------------------------------
User-installed lines are most commonly 2-wire lines, similar
to the 2-wire lines that connect residential phones to the
public switched network.

If you are leasing a line from the telephone company,
request a 2-wire line, the type of line the modem is
designed to work with.  If the telephone company only makes
a 4-wire line available, you'll need a 4-wire to 2-wire
converter at each end of the connection.  If the phone
company does not install the converters, you will have to
supply them.

For optimal operations, we recommend that the physical
length of these lines not exceed 5 miles.

Setting the Modem
-----------------
If the Courier is set to &L1, as described in what follows,
and the remote AT-compatible modem has a comparable setting,
they automatically connect when they are powered on.  They
also reconnect, without any operator intervention, if a
disturbance on the line is severe enough to break the
connection.

Set the modem as follows:

1.   Set your terminal or communications software to the
     rate at which you want the modems to communicate.  For
     example, use a terminal/software setting of 19.2K bps
     and, if both modems have the capability, they will
     connect at 14.4K bps.  The following instructions
     assume that you are familiar with the guidelines on
     using the &B and &H commands (Chapter 3) and the &W
     command (Chapter 3).

2.   Send the modem the following command:
          AT &B1 &S2 &H1 &L1 &W <Enter>

     &B1 fixes the modem's computer interface rate at
     19.2K bps.  &S2 causes the modem to send a Clear
     to Send (CTS) signal only after it sends the
     Carrier Detect (CD) signal, that is, only after it
     connects with the remote modem.  (See the note
     that follows.)  &H1 enables hardware (CTS) flow
     control.

     &L1 forces the modems off hook at power on and
     enables them to re-establish the connection should
     it be broken.  &W writes the settings to
     nonvolatile memory (NVRAM) as power-on defaults.

     NOTE:  We recommend using the &S2 setting, to
     delay CTS until after the connection is made, as a
     precaution.  If the modems are in the process of
     connecting or reconnecting, the Courier interprets
     any keyboard data entry, including an accidental
     key stroke, as a key-press abort, and hangs up.
     Delaying CTS until after carrier detection
     prevents this from happening, for example, if you
     are typing data to the remote modem when the
     modems momentarily disconnect and begin to
     reconnect.  However, you have to set the modem for
     hardware flow control, &H1.

     If your software or machine does not support Clear
     to Send (CTS), don't include &S2 and &H1 in the
     command string as suggested above.  Follow the
     Transmit Data flow control (&H) guidelines in
     Chapter 3.  But keep in mind that if the modems
     fail to connect or reconnect, the reason could be
     a key-press abort.

3.   Set the modem to load NVRAM settings at power-on, DIP
     switch 10 OFF.  It does not matter if the modem is in
     Dumb or Smart mode (DIP switch 8).
4.   Decide which modem is to be the calling modem and which
     the answering modem.  Set the answering modem to Auto
     Answer, DIP switch 5 OFF, and the calling modem to Auto
     Answer suppressed, DIP switch 5 ON.

5.   Power off and power on the modems.  This initiates the
     new DIP switch settings and loads the power-on
     defaults, including &L1.  The modems go off hook and
     establish the connection.

     NOTE:  If the modems cannot restore the connection and
     you could not set the modem to &S2, the reason could be
     a key-press abort.  If the problem persists, however,
     you may need to call your telephone company to have
     them check your line.






































+----------------------------------------------------------+
|                                                          |
|   APPENDIX F.  ADDITIONAL OPERATIONS                     |
|                                                          |
+----------------------------------------------------------+



CONTENTS
------------------------------------------------------------

HST Cellular
Voice/Data
Hewlett Packard 3000 Installations
MI/MIC Operations







































------------------------------------------------------------
CELLULAR OPERATIONS
------------------------------------------------------------

This function applies to Dual Standard HSTs only.  HST
cellular modems can be used to answer or originate calls,
but are proprietary.  They can only connect with other U.S.
Robotics Dual Standard modems with HST cellular
capabilities.

To enable cellular mode, load the factory setting template 3
by typing the following command.
          AT &F3 <Enter>

To save this as your power-on/default setting, type this:
          AT &F3 &W <Enter>

The &F3 command sets the serial port rate to 19,200 bps, and
formats the data for 8 bits, no parity and one stop bit.
The initialization string sent to the modem is shown below.
          AT B1 X7 S10 = 30 &B1 &L2 &H1 &I0 &R2

#    B1-enables HST modulation

#    X7-displays extended result codes including NO DIAL
     TONE, RINGING, NO ANSWER, and BUSY messages

#    &B1-sets the serial port rate so that it remains higher
     than the connection rate.

#    S10=30-sets the modem to wait 3 seconds after loss of
     carrier before hanging up.

#    &L2-enables cellular mode

#    &H1-enables hardware flow control

#    &I0-disables software flow control

#    &R2-sets the modem so it sends received data to the
     computer or terminal when the Ready To Send (RTS)
     signal is high, only if the computer or terminal
     supports RTS.

The modem uses the U.S. Robotics proprietary HST cellular
protocol to make connections.  The call starts at 1200 bps,
a V.42 error control connection is negotiated, then the
modem switches to 4800 bps and begins measuring the line
conditions.  Depending on line conditions, the modem
decreases or increases its connection rate, to a minimum
speed of 300 bps and a maximum of 12K bps.  If a connection
terminates before data transfer is completed, the system
tries to re-establish the link and complete the transfer.
If a large number of blocks are being resent (shown by the
ARQ LED flashing randomly; some software displays the blocks
retransmitted in the file transfer window), you may want to
reduce the packet size by doing the following:

1.   Be sure DIP switch 9 is ON so that the modem remains
     online if it receives +++.

2.   If DIP switch 9 is OFF, switch it to ON and reset the
     modem by issuing the ATZ command.

3.   Send the modem the escape sequence by typing +++ so
     that the transmission is interrupted, and wait 1
     second.

4.   Type AT S33=1 to reduce the packet size.

5.   Then type ATO so that the modem returns online and
     continues to transmit.

NOTE:  HST cellular connections can only be made with other
U.S. Robotics modems in HST cellular mode.  The modem cannot
be used to place a voice or data call to another phone or
modem when it is in this mode.

------------------------------------------------------------
VOICE/DATA
------------------------------------------------------------

The voice/data switch is located on the modem's front panel.
While the switch's primary function is to toggle back and
forth between voice and data communications, this feature
also allows you to perform other functions at the touch of a
switch.  Use Register S32 to select these functions, as
shown in Table F.1

Additionally, the Courier modem allows you to use the
voice/data switch to set the modem for remote configuration.
This is described in Remote Access in Appendix C.

NOTE:  Use the voice/data switch when the modem is in
Command mode (offline).  If you press the switch while the
modem is online, the modem hangs up and returns a NO CARRIER
result code.

Voice/Data Operations-S32=1, S32=2 or AT commands
-------------------------------------------------
When you install the Courier, you have the option of plug-
ging your phone into the second modular jack of the modem so
it's available for voice calls.  You can also switch between
the phone and modem during a call.

If the remote modem has handset exclusion, you can change
from voice to data and back again, with or without issuing a
command.

Handset exclusion means that if the modem is using the phone
line, your phone (handset) is automatically disconnected.
However, if you keep the handset off hook, once you hang up
the modem the handset takes over the phone line and you can
use voice communications again.  If the remote user does not
have handset exclusion, you may not be able to switch back
to voice mode successfully once you have switched to Data
mode.

The following instructions describe how to toggle voice/data
communications with the switch.  This is followed by
instructions for doing the same thing with AT commands.  If
the remote user does not have a switch, he or she can follow
the instructions for using the appropriate AT command.

Voice/Data Switch-S32=1, S32=2
-------------------------------

1.   Phone the other user to establish the bit rate, parity,
     word length and number of Stop bits the other person's
     modem accepts.  (Both modems should be offline, in
     Command mode.)

     You and the other user must also agree on which modem
     will go off hook in Originate mode and which in Answer
     mode.  To set the Courier for Originate mode, have S32
     set to 1.  The Answer modem should have S32 set to 2.

     NOTE:  By default the modem is shipped with S32 set to
     9.  If the stored command string command has been used
     (&ZC=s), the modem executes the string when the
     voice/data switch is pushed.  Otherwise, the modem acts
     like S32 is set to 1.

     Either party's device can be the originate or answer
     modem:  it doesn't matter who made the phone call.  But
     one modem must first enter Originate mode and the other
     then enter Answer mode.

2.   Without hanging up the phone, press the voice/data
     switch.

     If S32 is set to 2, Answer mode, press the voice/data
     switch immediately after the remote user forces the
     remote modem off hook in Originate mode.

3.   The other party should force the remote modem off hook
     in Answer mode by pressing the switch.

     If yours is the Answer modem (S32=2), the other party
     should press the voice/data switch immediately before
     you do so.

4.   If the remote modem has handset exclusion, the remote
     user should also keep the phone off hook in order to
     switch back to voice later.  If the remote modem
     doesn't have handset exclusion, you can try to switch
     back to voice later.  Or, you both can hang up your
     phones as soon as the modems go  off hook.

Software Commands-ATD, ATA
--------------------------
If your voice/data switch is set for a function other than
voice/data operations and you don't wish to change it, use
commands.

1.   Call the other user to establish the bit rate, parity,
     word length and number of Stop bits the other person's
     modem accepts.  Determine which modem will originate
     and which will answer.

2.   If you are to originate the connection, type the
     following command:
          ATD <Enter>

     NOTE:  Be sure the modem is not set to X2, X4, X6 or
     X7, or it will return the NO DIAL TONE result code and
     hang up.

3.   The other party must then have the remote modem go off
     hook in Answer mode.  The following command is used to
     do this:
          ATA <Enter>

4.   If the remote modem also has handset exclusion, leave
     both phones off hook in case you wish to switch back
     again to voice after your data transfer.  If the remote
     modem doesn't have handset exclusion, switching back to
     voice may not be successful.  If you don't want to
     switch back to voice later, hang up both phones as soon
     as the modems go off hook.

















Allowable Voice/Data Switch Functions
-------------------------------------
Use Register S32 to set the voice/data switch for the
function you desire.  The default is S32=9--the stored
command string is executed when the switch is pushed.  If a
string isn't stored, the modem acts like it's set to
S32=1--go off hook in Originate mode.  Pressing the switch
when you power on the modem causes it to perform a power-on
self-test.  See Table F.1-S32 Functions below.

S32                                     Related
Value     Voice/Data Switch Function    Command
------------------------------------------------------------
0         Disabled                      -
1         Voice/Data+Originate Mode     ATD
                                        (Appendix F)
2         Voice/Data+Answer Mode        ATA
                                        (Appendix F)
3         Redial Last Number            ATDL
                                        (Chapter 3)
4         Dial Number Stored at position 0    ATDS0
                                        (Chapter 3)
5         Auto Answer On/Off Toggle     ATS0=0 or 1
                                        (Chapter 3)
6              Reset Modem              ATZ
                                        (Chapter 3)
7         Initiate Remote Digital Loopback    AT&T6, S16=8
                                        (Appendix G)
8         Busy Out Phone Line Toggle    -    
9         Execute Stored Command (Default*)   AT&ZC=s
                                        (Chapter 3,
                                        Appendix E, F)

*    The modem is shipped from the factory set at S32=9.  If
     a command string has been stored (&ZC=s), the modem    
     executes the stored command string when the voice/data
     switch is pushed.  If no command string is stored, the
     modem acts like it is set to S32=1, Originate mode.

               Table F.1-S32 Functions













------------------------------------------------------------
HEWLETT PACKARD INSTALLATIONS
------------------------------------------------------------

During error control connections, the Courier recognizes the
ASCII ENQ/ACK characters exchanged between many Hewlett
Packard host computers and their terminals.  The HP host
sends the terminal an ENQ character at predefined intervals,
and sends no more data until the terminal responds with an
ACK character.

Courier modems manage this ENQ/ACK protocol so that
communication is speeded up, thereby enabling HP terminals
to achieve high speeds on dial-up lines.  Special flow
control settings, using the &I command, are required for HP
users.  These settings apply to ARQ connections only and to
Courier modems set to either B0 or B1.  Disregard other
Courier flow control commands.

Set the Courier to Host mode if it is attached to the host
computer, or to Terminal mode if it is attached to a
terminal, as follows:

     Host mode      AT&I3 <Enter>
     Terminal mode  AT&I4 <Enter>





























------------------------------------------------------------
MI/MIC operations
------------------------------------------------------------

DESCRIPTION
------------------------------------------------------------
Mode Indicate/Mode Indicate Common (MI/MIC) closure is
required by some installations whose existing hardware does
the dialing.  The modems do not Auto Dial.

In these situations, the modem must be forced off hook in
Originate mode.  This is done by shorting (closing) two of
the pins (not Tip and Ring) in the phone connector.  The
modem is then ready to go online and accept data when it
connects with the number dialed by the system equipment.

Courier modems are shipped with MI/MIC disabled, that is,
for normal use.  To set the modems for MI/MIC closure,
enable bit 5 of Register S34:  ATS34=32 or ATS34 .5=1.  We
recommend that you write that setting to NVRAM as a power-on
default.

Once you've set Register S34, have the system force the
modem off hook by closing the MI/MIC leads in the phone line
connector.  The modem's OH (Off Hook) status light, or LED,
goes on when the modem goes off hook.

TROUBLESHOOTING
-----------------------------------------------------------
You may find that the modem does not respond to MI/MIC
closure, which you can monitor by observing the LED.  Or the
modem may fail to go back on hook when the computer or
terminal drops the Data Terminal Ready (DTR) signal.  The
probable reason for either of these conditions is that your
phone equipment reverses MI/MIC polarity.

It's possible to solve this problem by reversing the modem's
MI/MIC wiring.  You'll have to dismantle the modem case and
reset two switches on the printed circuit board, as follows.

1.   Power off the modem and disconnect all of its cables.

2.   Turn the modem upside down.  Remove the two square
     vinyl feet near the back of the case, on either side of
     the bottom label's DIP switch diagram.  Be careful to
     put the vinyl feet aside, upside down, where they won't
     become stuck to another object.

3.   Remove the two Phillips screws located in the wells
     beneath the vinyl feet.

4.   Gently pry off the plastic volume slide-switch cover.

5.   Raise the back end of the case bottom until it is at
     about a 60 degree angle; lift it away from inside the
     front of the modem.  Put the case bottom aside.

6.   Locate the voice/data switch at the front of the modem.
     Lift up and remove the modem (printed circuit board),
     carefully easing the voice/data switch out of its
     opening in the front panel.

7.   Turn the modem rightside up and locate jumper switches
     J4 and J6, near the power-adaptor socket.

8.   The jumpers are black shunts that cover two out of
     three upright metal contacts.  As shown in the figure,
     the modem is shipped with the jumpers over the two
     contacts on each switch that are closest to the front
     panel.  The third contact on each switch is exposed.
     Lift off the jumpers from J4 and J6.  Reverse the
     positions.  That is, on each switch, cover the center
     and rightmost contacts.  Make sure the jumpers cover
     two contacts on each switch, or you'll disable the
     MI/MIC function.

9.   Replace the modem in the case top:  ease the voice/data
     switch into the opening in the front panel and make
     sure the back of the board rests on the locator pins at
     the rear (from which you removed the screws).

10.  Reconnect the modem's RS-232, power and phone cables,
     in that order.  Be sure the phone cable is plugged into
     the jack closest to the center of the modem-the jack
     represented by the wall jack icon on the case bottom
     label.

     CAUTION:  When you power on the modem there will be
     potentially hazardous voltage, particularly near the
     phone jacks.  Do not touch the board when the power is
     on.

11.  Power on the modem.  Try MI/MIC closure again.  Check
     to see that the Off Hook (OH) status light goes on.  If
     you dialed a number, listen for an answer tone from the
     remote modem.  Then drop the DTR signal.  The modem
     should go on hook and the OH status light should go
     off.

12.  If closure is not working properly, review the steps in
     this section.  Be sure the jumper switches are in the
     reverse position.  If you still have problems, there
     may be a problem with the phone cable.  Or there may be
     a problem with your hardware.

13.  When the equipment is working correctly, replace the
     bottom of the modem case.  Ease the two nibs near the
     front corners into their openings in the front of the
     case top, guide the rectangular slot over the volume
     switch, and ease the back of the case bottom into
     place.  Replace the two screws, the two vinyl feet, and
     the volume slide-switch cover.


















































+----------------------------------------------------------+
|                                                          |
|   APPENDIX G.  MODEM TESTING                             |
|                                                          |
+----------------------------------------------------------+

      Testing is available with the &T command or Register
      S16.  All loopback testing conforms to ITU-T
      Recommendation V.54.  Earlier U.S. Robotics high speed
      modems, however, did not perform the &T test
      repertoire.

      Only one test can be performed at a given time.  If
      you send a test command while the modem is in test
      mode, you'll receive an ERROR message.

      NOTE:  Testing is not available when the modem is in
      synchronous mode:  &M1, &M6, &M7.


TESTING WITH &T
------------------------------------------------------------

      The tests supported through the &T command include
      analog loopback, digital loopback and remote digital
      loopback.  Users can key in their own data during
      testing, or use the modem's internal test pattern and
      error detector.

      In all cases, disable error control before testing.
      If the modem is detecting errors and retransmitting
      the affected data, your results will be invalid.

      During testing, the MR status light flashes.


Ending a Test--&T0, S18
----------------------
      Issuing the &T0 command terminates a test.
      Alternatively, set Register S18 to a specified number
      of seconds, for example, S18=10.  When the 10 seconds
      are up, the modem automatically ends the test and
      returns to Command mode.  If the test was Analog
      Loopback, the &T0 command hangs the modem up.  If the
      test was Digital or Remote Digital Loopback, issue an
      ATH command to hang up the modem, or an ATZ command to
      hang up the modem and reset it to its defaults.

      NOTE:  If you use the S18 test timer, but in the pro-
      cess of testing you issue an ATZ command, S18 resets
      to zero and the timer is disabled.  You cannot store a
      value for S18 in nonvolatile memory:  its power-on and
      reset default is always zero.


ANALOG LOOPBACK--&T1, &T8
------------------------------------------------------------

      This test checks the operation of the modem's
      transmitter and receiver.

      There are two analog loopback options.  The first,
      &T1, involves your typing data that you can verify at
      your screen.

      The second option, &T8, is an internal self-test that
      does not involve the keyboard or screen.  It isolates
      the modem from the computer interface to give you a
      more specific result.

      NOTE:  Dual Standard modems must be set to B0
      (default) or tested at 2400 bps or lower to avoid HST
      asymmetrical modulation at higher speeds.

&T1
---
      1. If you are testing an HST or Dual Standard modem,
         set your terminal or software to 2400 bps.

      2. The modem must be in Command mode.  If you wish,
         set Register S18 as a test timer, as explained
         earlier.

      3. Send the modem the following command.

             AT &M0 &T1 <Enter>

         The modem disables error control, enters analog
         loopback (AL) mode, and sends a CONNECT message.
         The MR status light flashes.

      4. Type recognizable data so that you can verify it
         when it is looped back to the screen.

      5. End the test.  If you set S18, the modem automati-
         cally stops the test at the timeout, exits AL mode
         and responds OK.

         If you didn't set Register S18, wait one second and
         type +++ to bring the modem back to Command mode.
         If DIP switch 9 is OFF, the modem also hangs up and
         ends the test.

         If DIP switch 9 is ON, type AT&T0 to end the test.
         Or send either ATH or the command that resets the
         modem, ATZ.  The latter two commands end the test
         and hang up the modem.  The modem responds OK.  If

         the modem sends an ERROR message, you have issued
         an invalid command.

      6. If there were no errors, reset the modem to &M4,
         for error control, unless you've issued the ATZ
         reset command.

         NOTE:  If the modem is in online-command mode, that
         is, still connected to a remote modem, and you send
         it an &T1 or &T8 command, it drops the call, enters
         AL mode, sends a CONNECT result and waits for
         loopback characters.

&T8
---
      This AL option causes the modem to send an internal
      test pattern to its transmitter and loop it back to
      the receiver.  An internal error detector counts any
      errors and, when the test is ended, sends the number
      of errors or 000 (no errors) to the screen.

      Since you don't type anything during this test, and
      the modem does not send anything to the screen, this
      option verifies only the modem.  If there are no
      errors but your problem continues, it may be at the
      computer interface.

      1. If you are testing an HST or Dual Standard modem,
         set your terminal or software to 2400 bps.

      2. The modem must be in Command mode.  If you wish,
         set Register S18 as a test timer, as explained
         earlier.

      3. Send the modem the following command:

             AT &M0 &T8 <Enter>

         The modem disables error control and enters AL
         mode.  The MR status light flashes.  The modem
         sends its internal test pattern to the transmitter,
         and loops the pattern back to the receiver.  You
         will not see any data on your screen.

      4. End the test.  If you set S18, the modem automati-
         cally stops the test at the timeout.  If you didn't
         set Register S18, type AT&T0 to end the test.  Or
         use ATH or the command that resets the modem, ATZ.
         Both of the latter end the test and hang up the
         modem.

         The modem hangs up and returns a three-digit code,
         followed by OK.  A code of 000 indicates no errors
         were found.  A code of 255 indicates 255 or more
         errors.  An ERROR message indicates that you issued
         an invalid command.

      5. If there were no errors, reset the modem to &M4 for
         error control unless you issued the ATZ command.


&T2
---
      This option is reserved.


DIGITAL LOOPBACK--&T3
------------------------------------------------------------
      If your modem has passed the AL test, this test can
      help you locate a problem with a remote modem or the
      telephone channel.

      NOTE:  This test requires the modem to establish a
      connection and return to online-command mode in
      response to the +++ escape code.  DIP switch 9 must be
      set ON so that the modem does not hang up on receipt
      of the escape code.  After you change the switch,
      issue ATZ to the modem to initiate the new setting.

      As with AL testing, HST and Dual Standard modems
      should be tested at 2400 bps or lower.

      1. Set the modem to &M0, to disable error control.
         HST and Dual Standard modems should be set to 2400
         bps or lower to avoid asymmetrical modulation at
         higher speeds.  Establish a connection with the
         remote modem.

      2. Bring the modem back to Command mode with the +++
         escape code.  Then send it the AT&T3 command.  The
         modem enters DL mode and the MR status light
         flashes.

      3. The remote user should type a short message.  It
         will be looped back by your modem's transmitter for
         verification on the remote screen.  You will not
         see the message or any other data.

      4. When the remote user has completed the test, issue
         the AT&T0 command to end the test.  Or send either
         ATH or the command that resets the modem, ATZ.  The
         latter two commands end the test and hang up the
         modem.  The modem responds OK.  If the modem sends
         an ERROR message, you have issued an invalid
         command.

      5. Reset DIP switch 9 OFF if you normally use the

         factory default.  Reset the modem to &M4 unless you
         used the reset command, ATZ.


&T4, &T5
--------
      The &T4 option causes the modem to grant a remote
      modem's request for a Remote Digital Loopback test.

      The &T5 option cancels &T4, and the modem fails to
      recognize such a request.  This is the default so that
      your modem isn't subject to another user calling and
      tying up your modem without your permission.

REMOTE DIGITAL LOOPBACK--&T6, &T7
------------------------------------------------------------

      This test, like the local digital loopback test,
      verifies the condition of both modems and the phone
      link.

      The request for and granting of Remote Digital
      Loopback testing requires that both modems use ITU-T
      V.22 standard signaling.  The test must be performed
      at 2400 bps or lower.  If the remote modem does not
      have the capability or is not set to respond, you will
      get an ERROR result code.

      As with Analog Loopback, there are two Remote Digital
      Loopback options.  If you select &T6, you send
      keyboard data to the modem and verify it when it is
      returned over the phone lines and to your screen.  If
      you select &T7, the modem sends its internal test
      pattern and returns an error count to your screen.

      NOTE:  Both test options require the modem to
      establish a connection and return to online-command
      mode in response to the +++ escape code.  DIP switch 9
      must be set ON so that the modem does not hang up on
      receipt of the escape code.  If necessary, set the
      switch ON and then issue the ATZ command to the modem
      to initiate the new switch setting.

&T6
---
      1. Set the software to 2400 bps or lower.  Set the
         modem to &M0.  If you wish, set the S18 timer.

         Establish a connection with the remote modem.  If
         you haven't already done so, arrange with the
         remote user to cooperate with your testing and, if
         necessary, set the remote modem to acknowledge the
         RDL request.  For example, older U.S. Robotics high
         speed modems need to be set to S16=8.
      2. Bring the Modem back to Command mode with the +++
         escape code.  Send it the AT&T6 command.  The modem
         enters RDL mode and the MR status light flashes.

      3. Type a short message.  It will be looped back to
         your modem by the remote modem and to your screen
         for verification.  (The remote user will not see
         your data.)

      4. End the test.  If you set Register S18 the modem
         automatically ends the test when the test timeout
         is reached.  If you didn't set S18, type AT&T0 to
         end the test.  Or send either ATH or the command
         that resets the modem, ATZ.  The latter two
         commands end the test and hang up the modem.  The
         modem responds OK.  If you issue an invalid
         command, the modem sends an ERROR message.

         Data errors indicate a problem with the remote
         modem or the phone link.  If you have not performed
         analog loopback testing with your modem, the
         problem may also lie with your modem.

      5. Reset DIP switch 9 OFF unless you normally set that
         switch ON, and issue ATZ to the modem to initiate
         the new setting.  Reset the modem to &M4 unless you
         used the reset command, ATZ.

&T7
---
      This test option causes the modem to send an internal
      test pattern through the Remote Digital Loopback.  An
      internal error detector counts any errors and, when
      the test is ended, sends the number of errors or 000
      (no errors) to the screen.

      You don't need to type anything during this test.  The
      modem sends only its final error count to your screen.

      1. Set the software to 2400 bps or lower.  Set the
         modem to &M0.  If you wish, set the S18 timer.

         Establish a connection with the remote modem.  If
         you haven't already done so, arrange with the
         remote user to cooperate with your testing and, if
         necessary, set the remote modem to acknowledge the
         RDL request.  For example, older U.S. Robotics high
         speed modems need to be set to S16=8.

      2. Bring the modem back to Command mode with the +++
         escape code.  Then send it the AT&T7 command.  The
         modem enters RDL mode and the MR status light
         flashes.

         The modem sends its internal test pattern to the
         remote modem, which loops it back to your modem.
         You will not see the data on your screen.

      3. End the test.  If you set S18, the modem automati-
         cally stops the test when the timer times out.  If
         you didn't set Register S18, type AT&T0 to end the
         test.  Or send either ATH or the command that
         resets the modem, ATZ.  The latter two commands end
         the test and hang up the modem.  The modem responds
         OK.  If you issue an invalid command, the modem
         sends an ERROR message.

         When you terminate the test, the modem returns a
         three-digit code, followed by OK.  A code of 000
         indicates no errors were found.  A code of 255
         indicates 255 or more errors.

         If you've performed an Analog Loopback and know
         your modem is working properly, errors indicate a
         problem with either the phone connection or the
         remote modem.

      4. Reset DIP switch 9 OFF unless you normally operate
         with it ON.  Issue an ATZ command to initiate the
         new switch setting.  Reset the modem to &M4 unless
         you've sent it the ATZ reset command.


TESTING WITH REGISTER S16
------------------------------------------------------------

      Register S16 is a bit mapped register with the
      following bit functions:

      Bit Value Function
       0   1    Analog Loopback (AL)
       1   2    Dial Test
       2   4    Test Pattern
       3   8    Remote Digital Loopback (RDL)

      NOTE:  Earlier U.S. Robotics modems require bit 3 to
      be enabled in order to grant RDL to a remote modem.
      The modem now requires its default &T4 setting
      instead.  To perform RDL with a U.S. Robotics modem
      that does not use the &T test repertoire, that modem
      should be set to S16=8 before it can grant RDL
      testing.






ANALOG LOOPBACK (AL)--S16=1D
------------------------------------------------------------

      As with the &T AL test, do not attempt this test under
      error control.  HST and Dual Standard modems should be
      tested at 2400 bps or lower, to avoid asymmetrical
      modulation at higher speeds.

      To use the modem's Test Pattern (S16, bit 2) instead
      of typing your own data, see Test Pattern--S16=4 later
      in this appendix.

      1. To initiate testing, type AT&M0S16=1D.  The modem
         disables error control, enters AL mode and sends a
         CONNECT result code.  The MR status light flashes.

      2. Type data to the modem for the modem to transmit,
         loop to its receiver, and output to the screen.  An
         alternative is to use the Test Pattern, described
         later.

      3. End the test by not typing anything for one second,
         then typing three pluses (+++), and waiting another
         second.  This forces the modem back to Command
         mode.  If DIP switch 9 is OFF, the modem exits AL
         mode and returns to Command mode.  If DIP switch 9
         is ON, the modem maintains the connection when it
         receives the +++ escape code.  Issue the ATH
         command to end AL mode.

      4. Reset the modem to Data mode, S16=0, and error
         control (&M4), or issue the ATZ (reset) command.

DIAL TEST--S16=2
------------------------------------------------------------
      The Dial Test is used for factory testing the
      frequencies of tone values.  When S-Register 16 is set
      to 2 and a single tone is dialed (e.g., ATD7 <Enter>),
      the modem continues to transmit that tone until you
      type another Carriage Return.

TEST PATTERN--S16=4
------------------------------------------------------------
      The test pattern can be used instead of your typed
      data during Analog Loopback (AL) or Remote Digital
      Loopback (RDL), using &T commands or S16.  The test
      pattern is available at all speeds.  At 300 bps, the
      modem's serial port rate must be fixed (&B1) and the
      link rate fixed at 300 bps (&N1).  At rates over 9600
      bps, just set the modem for a fixed serial port rate
      (&B1).

      To use the test pattern during AL testing with S16,

      type the following command.  The test pattern is sent
      through the loopback.
             AT&M0S16=5D

      To use the test pattern during RDL testing with S16,
      type the following command.
             AT&M0S16=12

      To use the test pattern with the &T AL or RDL tests,
      insert the test pattern command, S16=4, before issuing
      the test command.  The first of the following commands
      initiates AL, the second RDL:
             ATS16=4&T1
             ATS16=4&T6

      The test pattern alone (ATS16=4) is used for testing
      equipment and the phone line.  When S16 is set to 4,
      the modem transmits the test pattern upon connection
      with a remote modem.

Ending Testing with the Test Pattern
---------------------------------------
      Pressing any character key cancels all test pattern
      tests and hangs up the modem.  If you used Register
      S16, be sure to reset Register S16 to Data mode when
      you reset the modem to its error control defaults, for
      example, ATZ or AT&M4S16=0.

REMOTE DIGITAL LOOPBACK--S16=8
------------------------------------------------------------

Responding Modem
----------------
      The responding modem must be ready to act on the
      Courier's RDL request.  U.S. Robotics high speed
      modems should be set to &T4.  If they do not have &T
      testing capability, they should be set to S16=8.

Initiating Modem
----------------

      1. If DIP switch 9 is OFF, set it ON so that it does
         not hang up on receipt of the +++ escape code.
         Issue an ATZ command to initiate the new switch
         setting.

      2. Set the software to 2400 or 1200 bps.  The ITU-T-
         specified RDL signals are defined only for
         connections at 2400 or 1200 bps.

      3. Disable error control by setting the modem to &M0.
         Then establish a connection with the remote modem.

      4. Bring the modem back to Command mode by sending it
         the escape code:  one second of no data, three
         pluses (+++), and another second of no data.

      5. When the OK result code appears, send the modem the
         following command.
               ATS16=8 O

         The modem enters RDL mode (S16=8), the MR status
         light flashes, and the modem goes back online (O
         command).  Then it transmits the ITU-T-defined RDL
         signals, causing the remote modem to enter RDL
         mode.

      6. Type any data at the keyboard.  (Or send the test
         pattern.)

      7. To end the test, send the modem the +++ escape code
         again to bring it back to Command mode.

      8. When the modem sends the OK result, reset the modem
         to Data mode with the following command.
               ATS16=0

         The modem signals the responding modem that RDL
         testing is over.  Terminate the call as you nor-
         mally would, and reset the modem to its normal
         error control setting, &M4 or &M5.

         Or, if you wish to resume data transmission with
         the remote modem, add the O command to the ATS16=0
         string to return the modem online.  Keep in mind,
         however, that error control is disabled.  Because
         error control is negotiated during the connection
         sequence, its status cannot be changed until the
         modem is back on hook and in Command mode.



















+----------------------------------------------------------+
|                                                          |
|   APPENDIX H.  GLOSSARY                                  |
|                                                          |
+----------------------------------------------------------+


Cross-references in the following definitions enclosed in
quotes.

Analog Loopback
---------------
A modem self-test in which data from the keyboard is sent to
the modem's transmitter, modulated into "analog" form,
looped back to the receiver, demodulated into "digital"
form, and returned to the screen for verification.

Analog Signals
--------------
Continuous, varying waveforms such as the voice tones car-
ried over phone lines.  Contrast with "digital signals."

Answer Mode
-----------
A state in which the modem transmits at the predefined high
frequency of the communications channel and receives at the
low frequency.  The transmit/receive frequencies are the re-
verse of the calling modem which is in "Originate mode."

Application (application program)
---------------------------------
A computer program designed to perform a specific function,
such as a word processor or a spreadsheet.

ARQ
---
Automatic Repeat Request.  A general term for error control
protocols which feature error detection and automatic
retransmission of defective blocks of data.  See "HST,"
"MNP," and "V.42."

ASCII
-----
American Standard Code for Information Interchange.  A 7-bit
binary code (0's, 1's) used to represent letters, numbers,
and special characters such as $, !, and /.  Supported by
almost every computer and terminal manufacturer.

Asymmetrical Modulation
-----------------------
A duplex transmission technique which splits the communi-
cations channel into one high speed channel and one slower
channel.  During a call under asymmetrical modulation, the
modem with the greatest amount of data to transmit is allo-
cated the high speed channel.  The modem with less data is
allocated the slow, or back channel (450 bps).  The modems
dynamically reverse the channels during a call if the volume
of data transfer changes.

Asynchronous Transmission
-------------------------
Data transmission in which the length of time between
transmitted "characters" may vary.

Because the time lapses between transmitted characters are
not uniform, the receiving modem must be signaled as to when
the data bits of a character begin and when they end.  The
addition of "Start" and "Stop bits" to each character serves
this purpose.

Auto Answer
-----------
A feature in modems enabling them to answer incoming calls
over the phone lines without the use of a telephone
receiver.

Auto Dial
---------
A feature in modems enabling them to dial phone numbers over
the phone system without the use of a telephone transmitter.

Baud Rate
---------
The number of discrete signal events per second occurring on
a communications channel.  Although not technically accu-
rate, baud rate is commonly used to mean "bit rate."

Bisync
------
Binary Synchronous Control.  An earlier protocol developed
by IBM for software applications and communicating devices
operating in synchronous environments.  The protocol defines
operations at the link level of communications, for example,
the format of data "frames" exchanged between modems over a
phone line.  See "Protocol," "HDLC," "SDLC."

Binary Digit
------------
A 0 or 1, reflecting the use of a binary numbering system
(only two digits).  Used because the computer recognizes
either of two states, OFF or ON.  Shortened form of binary
digit is "bit."

Bit Rate
--------
The number of "binary digits," or bits, transmitted per
second ("BPS").  Communications channels using telephone

channel modems are established at set bit rates, commonly
300, 1200, 2400, 4800, 9600, and 14400.

BPS
---
The bits ("binary digits") per second rate.

Buffer
------
A memory area used as temporary storage during input and
output operations.  An example is the modem's command
buffer.   Another is the Transmit Data flow control buffer
used for flow control and to store copies of transmitted
"frames" until they are positively acknowledged by the
receiving modem.

Byte
----
A group of "binary digits" stored and operated upon as a
unit.  A byte may have a coded value equal to a character in
the ASCII code (letters, numbers), or have some other value
meaningful to the computer.  In user documentation, the term
usually refers to 8-bit units or characters.  1 kilobyte (K)
is equal to 1,024 bytes or characters; 64K indicates 65,536
bytes or characters.

Carrier
-------
A continuous frequency capable of being either modulated or
impressed with another information-carrying signal.
Carriers are  generated and maintained by modems via the
transmission lines of the telephone companies.

CCITT
-----
Formerly, an international organization that defined
standards for telegraphic and telephone equipment.  It has
been incorporated into its parent organization,
International Telecommunication Union ("ITU").
Telecommunication standards are now covered under
Telecommunications Standards Sector (TSS).  ITU-T replaces
CCITT.  For example, the Bell 212A standard for 1200 bps
communication in North America was referred to as CCITT
V.22.  It is now referred to as ITU-T V.22.

Character
---------
A representation, coded in "binary digits," of a letter,
number, or other symbol.

Characters Per Second
---------------------
A data transfer rate generally estimated from the "bit rate"
and the "character length."

For example, at 2400 bps, 8-bit characters with "Start" and
"Stop bits" (for a total of ten bits per character) will be
transmitted at a rate of approximately 240 characters per
second (cps).  Some protocols, such as USR-HST and MNP,
employ advanced techniques such as longer transmission
"frames" and "data compression" to increase cps.

Class 1/EIA-578
---------------
An American standard used between facsimile application
programs and facsimile modems for sending and receiving
Class 1 faxes.

Class 2.0/EIA-592
-----------------
An American standard used between facsimile application
programs and facsimile modems for sending and receiving
Class 2.0 faxes.

Cyclic Redundancy Checking (CRC)
--------------------------------
An error-detection technique consisting of a cyclic
algorithm performed on each block or frame of data by both
sending and receiving modems.  The sending modem inserts the
results of its computation in each data block in the form of
a CRC code.  The receiving modem compares its results with
the received CRC code and responds with either a positive or
negative acknowledgment.  In the ARQ protocol implemented in
U.S. Robotics high speed modems, the receiving modem accepts
no more data until a defective block is received correctly.

Data Communications
-------------------
A type of communications in which computers and terminals
are able to exchange data over an electronic medium.

Data Compression
----------------
When the transmitting modem detects redundant units of data,
it recodes them into shorter units of fewer bits.  The
receiving modem then decompresses the redundant data units
before passing them to the receiving computer.

Data Compression Table
----------------------
A table of values assigned for each character during a call
under data compression.  Default values in the table are
continually altered and built during each call:  the longer
the table, the more efficient throughput gained.
If a destructive Break is sent during a call (see the &Y
command), causing the modems to reset the compression
tables, you can expect diminished throughput.

Data Mode
---------
The mode in which the fax modem is capable of sending and
receiving data files.  A standard modem without fax
capabilities is always in Data mode.

DCE
---
Data Communication (or Circuit-Terminating) Equipment.  In
this manual, the term applies to dial-up modems that estab-
lish and control the data link via the telephone network.

Dedicated Line
--------------
A user-installed telephone line used to connect a specified
number of computers or terminals within a limited area, for
example, one building.  The line is a cable rather than a
public-access telephone line.  The communications channel
may also be referred to as nonswitched because calls do not
go through telephone company switching equipment.

Default
-------
Any setting assumed, at startup or reset, by the computer's
software and attached devices, and operational until changed
by the user.

Digital Loopback
----------------
A test that checks the modem's RS-232 interface and the
cable that connects the terminal or computer and the modem.
The modem receives data (in the form of "digital signals")
from the computer or terminal, and immediately returns the
data to the screen for verification.

Digital Signals
---------------
Discrete, uniform signals.  In this manual, the term refers
to the "binary digits" 0 and 1.

Duplex
------
Indicates a communications channel capable of carrying
signals in both directions. See "Half Duplex," "Full
Duplex."

EIA
---
Electronic Industries Association, which defines electronic
standards in the U.S.

Equalization
------------
A compensation circuit designed into modems to counteract
certain distortions introduced by the telephone channel.
Two types are used:  fixed (compromise) equalizers and those
that adapt to channel conditions.  U.S. Robotics high speed
modems use adaptive equalization.

Error Control
-------------
Various techniques which check the reliability of characters
("parity") or blocks of data.  V.42, MNP and HST error
control protocols use error detection ("CRC") and
retransmission of errored frames ("ARQ").

Facsimile
---------
A method for transmitting the image on a printed page from
one point to another.  Commonly referred to as Fax.

Fax Mode
--------
The mode in which the fax modem is capable of sending and
receiving files in a facsimile format.

Flow Control
------------
A mechanism that compensates for differences in the flow of
data input to and output from a modem or other device.

Frame
-----
A data communications term for a block of data with header
and trailer information attached.  The added information
usually includes a frame number, block size data, error-
check codes, and Start/End indicators.

Full Duplex
-----------
Signal flow in both directions at the same time.  In micro-
computer communications, may refer to the suppression of the
online "Local Echo."

Half Duplex
-----------
Signal flow in both directions, but only one way at a time.
In microcomputer communications, may refer to activation of
the online "Local Echo," which causes the modem to send a
copy of the  transmitted data to the screen of the sending
computer.

HDLC
----
High Level Data Link Control.  A standard protocol developed
by the International Standards Organization for software
applications and communicating devices operating in
synchronous environments.  The protocol defines operations
at the link level of communications, for example, the format
of data "frames" exchanged between modems over a phone line.
See "Bisync," "Protocol," "SDLC."

HST
---
High Speed Technology, U.S. Robotics' proprietary signaling
scheme, design and error control protocol for high-speed
modems.  HST incorporates trellis-coded modulation, for
greater immunity from variable phone line conditions, and
asymmetrical modulation for more efficient use of the phone
channel at speeds of 4800 bps and above.  HST also incorpo-
rates "MNP"-compatible error control procedures adapted to
asymmetrical modulation.

Hz
--
Hertz, a frequency measurement unit used internationally to
indicate one cycle per second.

ITU-T
-----
International Telecommunication Union-Telecommunication
sector.  Formerly referred to as CCITT.  An international
organization that defines standards for telegraphic and
telephone equipment.  For example, the Bell 212A standard
for 1200 bps communication in North America is observed
internationally as ITU-T V.22.  For 2400 bps communication,
most U.S. manufacturers observe V.22 bis.

LAPM
----
Link Access Procedure for Modems, an error control
"protocol" incorporated in ITU-T Recommendation V.42.  Like
the "MNP" and "HST" protocols, LAPM uses cyclic redundancy
checking ("CRC") and retransmission of corrupted data
("ARQ") to ensure data reliability.

Local Echo
----------
A modem feature that enables the modem to send copies of
keyboard commands and transmitted data to the screen.  When
the modem is in Command mode (not online to another system)
the local echo is invoked through the ATE1 command.  The
command causes the modem to display your typed commands.
When the modem is online to another system, the local echo
is invoked through the ATF0 command.  This command causes
the modem to display the data it transmits to the remote
system.

MI/MIC
------
Mode Indicate/Mode Indicate Common, also called Forced or
Manual Originate.  Provided for installations where other
equipment, rather than the modem, does the dialing.  In such
installations, the modem operates in Dumb mode (no Auto Dial
capability), yet must go off hook in "Originate mode" to
connect with answering modems.

MNP
---
Microcom Networking Protocol, an asynchronous error control
protocol developed by Microcom, Inc. and now in the public
domain.  The protocol ensures error-free transmission
through error detection ("CRC") and retransmission of
errored frames.  U.S. Robotics modems use MNP Levels 1-4 and
Level 5 data compression.  MNP Levels 1-4 have been
incorporated into ITU-T Recommendation V.42.  Compare "HST."

Modem
-----
A device that transmits/receives computer data through a
communications channel such as radio or telephone lines.
The Courier is a telephone channel modem that modulates, or
transforms, "digital signals" from a computer into the
"analog" form that can be carried successfully on a phone
line.  It also demodulates signals received from the phone
line back to digital signals before passing them to the
receiving computer.

Nonvolatile Memory (NVRAM)
--------------------------
User-programmable random access memory whose data is
retained when modem power is turned off.  Used in Courier
modems to store a user-defined default configuration loaded
into random access memory ("RAM") at power on.

OFF/ON Hook
-----------
Modem operations which are the equivalent of manually lift-
ing a phone receiver (taking it off hook) and replacing it
(going on hook).

Online Fallback
---------------
A feature that allows high speed error-control modems to
monitor line quality and fall back to the next lower speed
if line quality degrades.  The modems fall forward as line
quality improves.


Originate Mode
--------------
A state in which the modem transmits at the predefined low
frequency of the communications channel and receives at the
high frequency.  The transmit/receive frequencies are the
reverse of the called modem which is in "Answer mode."


Parallel Transmission
---------------------
The transfer of data characters using parallel electrical
paths for each bit of the character, for example, 8 paths
for 8-bit characters.  Data is stored in computers in
parallel form, but may be converted to serial form for
certain operations.  See "Serial Transmission."

Parity
------
An error-detection method that checks the validity of a
transmitted character.  Character checking has been
surpassed by more reliable and efficient forms of block-
checking, including "Xmodem"-type protocols and the "ARQ"
protocol implemented in Courier modems.

The same type of parity must be used by two communicating
computers, or both may omit parity.  When parity is used, a
parity bit is added to each transmitted character.  The
bit's value is 0 or 1, to make the total number of 1's in
the character even or odd, depending on which type of parity
is used.

Protocol
--------
A system of rules and procedures governing communications
between two or more devices.  Protocols vary, but communi-
cating devices  must follow the same protocol in order to
exchange data.  The format of the data, readiness to receive
or send, error detection and error correction are some of
the operations that may be defined in protocols.

RAM
---
Random Access Memory.  Memory that is available for use when
the modem is turned on, but that clears of all information
when the power is turned off.  The modem's RAM holds the
current operational settings, a flow control "buffer," and a
command buffer.

Remote Access
-------------
A feature that allows a remotely-located user to view the
Courier's configuration screens and change the Courier's
configuration.  Password protection is available.


Remote Digital Loopback
-----------------------
A test that checks the phone link and a remote modem's
transmitter and receiver.  Data entered from the keyboard is
transmitted from the initiating modem, received by the
remote modem's receiver, looped through its transmitter, and
returned to the local screen for verification.
Remote Echo
-----------
A copy of the data received by the remote system, returned
to the sending system and displayed on the screen.  Remote
echoing is a function of the remote system.

ROM
---
Read Only Memory.  Permanent memory, not user-programmable.
The Courier's factory settings are stored in ROM and can be
read (loaded) into RAM as an operational configuration if
DIP switch S10 is ON at power on.

Serial Transmission
-------------------
The transfer of data characters one bit at a time,
sequentially, using a single electrical path.  See "Parallel
Transmission."

Start/Stop Bits
---------------
The signaling bits attached to a character before the
character is transmitted during "Asynchronous Transmission."

SDLC
----
Synchronous Data Link Control.  A protocol developed by IBM
for software applications and communicating devices
operating in IBM's Systems Network Architecture (SNA).  The
protocol defines operations at the link level of communi-
cations, for example, the format of data "frames" exchanged
between modems over a phone line.  See "Bisync," "Protocol,"
"HDLC."

Synchronous Transmission
------------------------
A form of transmission in which blocks of data are sent at
strictly timed intervals.  Because the timing is uniform, no
"Start" or "Stop bits" are required.  Compare "Asynchronous
Transmission."

Some mainframes only support synchronous communications
unless their owners have installed a synchronous adapter and
appropriate software.


Terminal
--------
A device whose keyboard and display are used for sending and
receiving data over a communications link.  Differs from a
microcomputer in that it has no internal processing capa-
bilities.  Used to enter data into or retrieve processed
data from a system or network.

Terminal Mode
-------------
An operational mode required for microcomputers to transmit
data.  In Terminal mode the computer acts as if it were a
standard terminal such as a teletypewriter, rather than a
data processor.  Keyboard entries go directly to the modem,
whether the entry is a modem command or data to be trans-
mitted over the phone lines.  Received data is output
directly to the screen.  The more popular communications
software products control Terminal mode as well as enable
more complex operations, including file transmission and
saving received files.

Throughput
----------
The amount of actual user data transmitted per second with-
out the overhead of protocol information such as Start and
Stop bits or frame headers and trailers.  Compare
"characters per second."

Transmission Rate
-----------------
Same as "Bit Rate."

V.21-Fax
--------
An "ITU-T" standard for facsimile operations at 300 bps.
U.S. Robotics or compatible fax devices then transmit or
receive at higher speeds.

V.21-Modem
----------
An "ITU-T" standard for modem communications at 300 bps.
Modems made in the U.S. or Canada follow the Bell 103 stan-
dard.  However, the modem can be set to answer V.21 calls
from overseas.

V.22
----
An "ITU-T" standard for modem communications at 1200 bps,
compatible with the Bell 212A standard observed in the U.S.
and Canada.

V.22 bis  
--------
An "ITU-T" standard for modem communications at 2400 bps.
The standard includes an automatic link negotiation fallback
to 1200 bps and compatibility with Bell 212A/V.22 modems.

V.23
----
An "ITU-T" standard for modem communications at 1200 bps
with a 75 bps back channel.  Used in the U.K.


V.25
----
An "ITU-T" standard for modem communications that specifies
an answer tone different from the Bell answer tone used in
the U.S. and Canada.  All U.S. Robotics modems can be set
with the B0 command so that they use the V.25 2100 Hz tone
when answering overseas calls.

V.25 bis
--------
An "ITU-T" standard for synchronous communications between
the mainframe or host and the modem using the HDLC or
character-oriented protocol.  Modulation depends on the
serial port rate and setting of the transmitting clock
source, &X.

V.27 ter
--------
An "ITU-T" standard for facsimile operations that specifies
modulation at 4800 bps, with fallback to 2400 bps.

V.17
----
An "ITU-T" standard for facsimile operations that specifies
modulation at 14.4K bps, with fallback to 12K bps.

V.29
----
An "ITU-T" standard for facsimile operations that specifies
modulation at 9600 bps, with fallback to 7200 bps.

V.32
----
An "ITU-T" standard for modem communications at 9600 bps and
4800 bps.  V.32 modems fall back to 4800 bps when line
quality is impaired, and fall forward again to 9600 bps when
line quality improves.

V.32 bis
--------
A "ITU-T" standard that extends the V.32 connection range:
4800, 7200, 9600, 12K and 14.4K bps.  V.32 bis modems fall
back to the next lower speed when line quality is impaired,
and fall back further as necessary.  They fall forward to
the next higher speed when line quality improves.

V.42
----
A "ITU-T" standard for modem communications that defines a
two-stage process of detection and negotiation for LAPM
error control.  V.42 also supports the MNP error control
protocol, levels 1-4.
V.42 bis
--------
An extension of "ITU-T" V.42 that defines a specific data
compression scheme for use with V.42 and MNP error control.

Word Length
-----------
The number of bits in a data character without parity, start
or stop bits.

Xmodem
------
The first of a family of error control software "protocols"
used to transfer files between modems.  These protocols are
in the public domain and are available from many bulletin
board services.

XON/XOFF
--------
Standard "ASCII" control characters used to tell an
intelligent device to stop/resume transmitting data.  In
most systems typing <Ctrl>-S sends the XOFF character.  Some
devices, including the Courier, understand <Ctrl>-Q as XON;
others interpret the pressing of any key after <Ctrl>-S as
XON.





























+----------------------------------------------------------+
|                                                          |
|    APPENDIX I.  TECHNICAL SPECIFICATIONS                 |
|                                                          |
+----------------------------------------------------------+

U.S. ROBOTICS HIGH SPEED TECHNOLOGY (HST)
------------------------------------------------------------
16.8K, 14.4K, 12K, 9600, 7200 bps, synchronous/asynchronous,
asymmetrical, 450 bps back channel with automatic handshake
adjustment to 300 bps, Trellis Coded Modulation (TCM),
Quadrature Amplitude Modulation (QAM)

4800 bps, synchronous/asynchronous, asymmetrical, 450 bps
back channel with automatic handshake adjustment to 300 bps,
Quadrature Amplitude Modulation (QAM)

U.S. ROBOTICS V.32 TERBO
------------------------------------------------------------
21.6K, 19.2K, 16.8K, 14.4K. 12K, 9600, 7200 bps
asynchronous, 19.2K, 16.8K, 14.4K. 12K, 9600, 7200 bps
synchronous, Trellis Coded Modulation (TCM)
4800 bps, synchronous/asynchronous, Quadrature Amplitude
Modulation (QAM)

ADDITIONAL COMPATIBILITY FEATURES

ITU-T V.32 bis, 14400, 9600 bps, synchronous, asynchronous,
Trellis Coded Modulation (TCM); 4800 bps, synchronous,
asynchronous, Quadrature Amplitude Modulation (QAM)

ITU-T V.32, 9600 bps, synchronous, asynchronous, Trellis
Coded Modulation (TCM); 4800 bps, synchronous, asynchronous,
Quadrature Amplitude Modulation (QAM)

ITU-T V.25 2100 Hz tone

ITU-T V.23, 1200 bps, asymmetrical (1200/75 bps), Frequency
Shift Keying (FSK)

ITU-T V.22 bis, 2400 bps, synchronous/asynchronous,
Quadrature Amplitude Modulation (QAM)

ITU-T V.22, 1200 bps, synchronous/asynchronous, Differential
Phase Shift Keying (DPSK)

Bell 212A, 1200 bps, synchronous/asynchronous, Differential
Phase Shift Keying (DPSK)

Bell 103, 300 bps, asynchronous, Frequency Shift Keying
(FSK)

ITU-T V.21, 300 bps, asynchronous, Frequency Shift Keying
(FSK)
U.S. Robotics HST error control protocol, asymmetrical mode,
at 16.8K, 14.4K, 12K, 9600, 7200, 4800 bps, 450/300 bps back
channel

ITU-T V.42 error control protocol at 14.4K, 12K, 9600, 7200,
4800 bps (V.32 bis mode) and at 2400/1200 bps

ITU-T V.42 bis data compression (all modes and speeds of
1200 bps and higher)

Microcom Networking Protocol (MNP) error control protocol,
Levels 2-4 at 14.4K, 12K, 9600, 7200, 4800 bps (V.32 bis
mode) and at 2400/1200 bps

Microcom Networking Protocol (MNP) Level 5 data compression
(all modes and speeds of 1200 bps and higher)

DB-25 RS-232 terminal/modem interface

Superset of industry standard AT command set, S-registers,
DIP switches

Optional MI/MIC closure

Optional pulsed DSR

ITU-T V.32 BIS
------------------------------------------------------------
14.4K. 12K, 9600, 7200 bps, synchronous/asynchronous,
Trellis Coded Modulation (TCM)

4800 bps, synchronous/asynchronous, Quadrature Amplitude
Modulation (QAM)

ADDITIONAL COMPATIBILITY FEATURES

ITU-T V.32, 9600 bps, synchronous, asynchronous, Trellis
Coded Modulation (TCM); 4800 bps, synchronous, asynchronous,
Quadrature Amplitude Modulation (QAM)

ITU-T V.25 2100 Hz tone

ITU-T V.23, 1200 bps, asymmetrical (1200/75 bps), Frequency
Shift Keying (FSK)

ITU-T V.22 bis, 2400 bps, synchronous/asynchronous,
Quadrature Amplitude Modulation (QAM)

ITU-T V.22, 1200 bps, synchronous/asynchronous, Differential
Phase Shift Keying (DPSK)

Bell 212A, 1200 bps, synchronous/asynchronous, Differential
Phase Shift Keying (DPSK)

Bell 103, 300 bps, asynchronous, Frequency Shift Keying
(FSK)

ITU-T V.21, 300 bps, asynchronous, Frequency Shift Keying
(FSK)
U.S. Robotics HST error control protocol, asymmetrical mode,
at 16.8K, 14.4K, 12K, 9600, 7200, 4800 bps, 450/300 bps back
channel

ITU-T V.42 error control protocol at 14.4K, 12K, 9600, 7200,
4800 bps (V.32 bis mode) and at 2400/1200 bps

ITU-T V.42 bis data compression (all modes and speeds of
1200 bps and higher)

Microcom Networking Protocol (MNP) error control protocol,
Levels 2-4 at 14.4K, 12K, 9600, 7200, 4800 bps (V.32 bis
mode) and at 2400/1200 bps

Microcom Networking Protocol (MNP) Level 5 data compression
(all modes and speeds of 1200 bps and higher)

DB-25 RS-232 terminal/modem interface

Superset of industry standard AT command set, S-registers,
DIP switches

Optional MI/MIC closure

Optional pulsed DSR

SERIAL PORT RATES
------------------------------------------------------------
115.2K, 57.6K, 38.4K, 19.2K, 9600, 4800, 2400, 1200, 300 bps
Link Rates
Data mode:     V.32 terbo:  21.6K, 19.2K, 16.8K bps
               HST:  16.8K bps
               Both:  14.4K, 12K, 9600, 7200, 4800, 2400,
               1200, 300 bps
Fax mode:      14.4K, 12K, 9600, 7200, 4800, 2400, 300 bps

ADAPTIVE SPEED LEVELING
------------------------------------------------------------
21.6K, 19.2K, 16.8K, 14.4K, 12K, 9600, 7200, 4800 bps

PHONE LINE INTERFACE
------------------------------------------------------------
RJ11, RJ45S phone jacks

COMMUNICATIONS CHANNEL
------------------------------------------------------------
Full/half duplex on 2-wire dial-up, dedicated, or leased
phone lines; demand-driven high speed channel turnaround in
HST mode; symmetrical speeds in V.32 bis mode
OPERATIONAL MODES
------------------------------------------------------------
Synchronous/Asynchronous, Auto Dial/Answer, Manual
Originate/Answer, Smart/Dumb mode, Auto Dial/Auto Answer,
Auto Answer only, Forced Originate (MI/MIC)

Fax Modems:  The above modes plus fax mode

FAX SERVICE CLASS 1 COMMANDS
------------------------------------------------------------
+FCLASS=n (0,1)     Class identification and control
+FTS=n (0,255)      Stop transmission and pause, 10ms.
+FRS=n (0,255)      Wait for silence, 10 ms.
+FTM=n (3,24,48,72,73,74,96,121,122,145,146)
                    Transmit data with carrier
+FRM=n (3,24,48,72,73,74,96,121,122,145,146)
                    Receive data with carrier
+FTH=n (3,24,48,72,73,74,96,121,122,145,146)
                    Transmit HDLC data with carrier
+FRH=n (3,24,48,72,73,74,96,121,122,145,146)
                    Receive HDLC data with carrier

FAX SERVICE CLASS 2.0 COMMANDS
------------------------------------------------------------
Class 2.0 fax commands are too numerous to be listed here.
For information on Class 2.0 technical specifications,
contact Global Engineering Documents, at 1-800-854-7179.
The document that covers this information is:
     ANSI/EIA/TIA-592-1993 (EIA-592)
     Asynchronous Facsimile DCE Control Standard
     May, 1993

Optional Class 2.0 FAX commands supported
-----------------------------------------
U.S. Robotics implements the following optional Class 2.0
fax commands :

+FNS=0,1            Pass-through non-Standard negotiation
                    byte string
+FCR=0,1            Capability to receive
+FAA=0,1            Adaptive Answer mode
+FCT=0-255 sec.     Phase C Timeout
+FHS=0-255          Hangup Status Code, read only
+FMS=0-3            Minimum Phase C Speed
+FBS?=500,100       Buffer size, read only

DIALING
------------------------------------------------------------
Dialing Rotary (pulse 0-9), Tone (DTMF 0-9, #, *), a-z when
in Quote (") Mode




DATA FORMAT
------------------------------------------------------------
Binary, serial; defaults to 8-bit word length, no parity,
and 1 stop bit
          Word      Parity         Stop
          Length    (1 Bit)        Bits
          ----------------------------
          7         Even, Odd      1
                    Mark, Space
          7         None           2
          8         None           1

V.25 BIS SYNCHRONOUS COMMANDS AND RESULT CODES
------------------------------------------------------------
Commands:
---------
Connect incoming call (CIC); Call request using number
provided (CRN); Call Request with memory location (CRS);
Disregard incoming call (DIC); Program number (PRNn);
Request list of forbidden numbers (RFN); Request list of
stored numbers (RLN).

Dial options:
-------------
0+9 & : > < = P T);

Result Codes:
-------------
Call failure indication (CFI) with optional parameters:
Abort call (CFAB); local modem busy (CFCB); Engaged tone
(CFET); Forbidden call (CFFC); Number not stored (CFNS);
Answer tone not detected (CFNT); Ring tone (CFRT); Connect
(CNX); List of numbers (LS); List of forbidden numbers
(LSF); List of stored numbers (LSN); Incoming call (INC);
Invalid (INV) with optional parameters:  Message syntax
error (INVMS); Command Unknown (INVCU); Parameter syntax
error (INVPS); Parameter value error (INVPV); Valid (VAL).

Commands and Result Codes not supported:
----------------------------------------
Call request with identification number (CRI); Program
identifier (PRI); Request list of identification numbers
(RLI); List of delayed call numbers (RLD).











FRONT PANEL STATUS LIGHTS
------------------------------------------------------------

HS   High Speed (above 2400 bps)
AA   Auto Answer/Answer
CD   Carrier Detect
OH   Off Hook
RD   Received Data
SD   Send Data
TR   Terminal Ready (DTR)
MR   Modem Ready/Test mode
RS   Request to Send
CS   Clear to Send
SYN  Synchronous mode
ARQ/ Error control connection established
FAX  Modem in Fax mode

FLOW CONTROL BUFFERS
------------------------------------------------------------
Transmit Buffer
     Error control:  3.25k bytes
     Non-Error control:  1.5k bytes, 128-byte option

Receive Buffer:  2K bytes

COMMAND BUFFER
------------------------------------------------------------
40 characters, exclusive of AT prefix, Carriage Return and
spaces

TEST OPTIONS
------------------------------------------------------------
     Analog loopback with test pattern
     Remote digital loopback
     Digital loopback
     Test pattern
     Dial test

CALL PROGRESS CODES
------------------------------------------------------------
     FAX
     DATA
     NO DIAL TONE
     BUSY
     NO ANSWER
     RINGING
     VOICE

FAILED CALL TIMEOUT
------------------------------------------------------------
60-sec. default, programmable 2-255 sec.



ANSWER TONE TIMEOUT
------------------------------------------------------------
60 sec.

ANSWER TONE DETECTOR
------------------------------------------------------------
2200-2300 Hz

LOSS OF CARRIER (DISCONNECT TIMER)
------------------------------------------------------------
0.7-sec. default, programmable 0.2-25.5 sec.

EQUALIZATION
------------------------------------------------------------
Adaptive

TRANSMITTER CARRIER FREQUENCIES
------------------------------------------------------------
USR-V.32 terbo
     Originate Mode:     1800 Hz
     Answer Mode:   1800 Hz

USR-HST, 450 bps back channel
     Originate Mode:     375 Hz
     Answer Mode:   1800 Hz

USR-HST, 300 bps back channel
     Originate Mode:     350 Hz
     Answer Mode:   1800 Hz

V.32 bis
     Originate Mode:     1800 Hz
     Answer Mode:   1800 Hz

V.23
     Originate Mode:     
     Mark:     390 Hz
     Space:    450 Hz
     Answer Mode:
     Mark:     1300 Hz
     Space:    2100 Hz
     
V.22 bis, V.22, Bell 212A
     Originate Mode:     1200 Hz
     Answer Mode:   2400 Hz

Bell 103
     Originate Mode:     
     Mark:     1270 Hz
     Space:    1070 Hz
     Answer Mode:
     Mark:     2225 Hz
     Space:    2025 Hz

V.21
     Originate Mode:
     Mark:     980 Hz
     Space:    1180 Hz
     Answer Mode:   
     Mark:     1650 Hz
     Space:    1850 Hz

RECEIVER CARRIER FREQUENCIES
------------------------------------------------------------
USR-V.32 terbo
     Originate Mode:     1800 Hz
     Answer Mode:   1800 Hz

USR-HST, 450 bps back channel
     Originate Mode:     1800 Hz
     Answer Mode:   375 Hz

USR-HST, 300 bps back channel
     Originate Mode:     1800 Hz
     Answer Mode:   350 Hz

V.32 bis
     Originate Mode:     1800 Hz
     Answer Mode:   1800 Hz

V.23
     Originate Mode:     
     Mark:     1300 Hz
     Space:    2100 Hz
     Answer Mode:
     Mark:     390 Hz
     Space:    450 Hz

V.22 bis, V.22, Bell 212A
     Originate Mode:     2400 Hz
     Answer Mode:   1200 Hz

Bell 103
     Originate Mode:     
     Mark:     2225 Hz
     Space:    2025 Hz
     Answer Mode:
     Mark:     1270 Hz
     Space:    1070 Hz

V.21
     Originate Mode:
     Mark:     1650 Hz
     Space:    1850 Hz
     Answer Mode:
     Mark:     980 Hz
     Space:    1180 Hz

RECEIVE SENSITIVITY
------------------------------------------------------------
- 44 dBm + 2 dBm

TRANSMIT LEVEL
------------------------------------------------------------
- 9 dBm maximum

TRANSMITTER FREQUENCY TOLERANCE
------------------------------------------------------------
.01%

CERTIFICATION
------------------------------------------------------------
FCC Part 68 and Part 15, Class B Domestic; DOC (Canada), UL
listed

POWER CONSUMPTION
------------------------------------------------------------
5 watts

SIZE
------------------------------------------------------------
6.25 x 10.25 x 1.5 inches





150


