





                                                                COURIER HST


          USRobotics is a registered trademark and Courier HST is a
          trademark of U.S. Robotics, Inc.  Touch-Tone is a trademark of
          American Telephone and Telegraph.  InterBridge is a trademark of
          Hayes Microcomputer Products, Inc.  MCI Mail is a service mark of
          MCI Communications, Inc.  Microcom Networking Protocol (MNP) is a
          trademark of Microcom, Inc.  Sprint is a trademark of General
          Telephone and Electric.

          

          

          TABLE OF CONTENTS

          Limited Warranty                                  vii
          FCC Registration Numbers                         viii
          Connecting to the Telephone Company              viii
          Radio and Television Interference                viii
          For Canadian Modem Users                           ix
          How to Use this Manual                              x
          

                         PART I.  INSTALLATION AND OPERATION
                                          
          CHAPTER 1 -- Introduction                         1-1

             Advanced Features
             The Courier Product Family
             Compatibility
             
          CHAPTER 2 -- Set-Up and Testing                   2-1

               Package Components
               Operational Requirements
               Assembling the Modem
               Testing
               
          CHAPTER 3 -- Operations at a Glance               3-1

               Data Format
               Error Control
               Data Compression
               Dialing
                    HST-Compatible, 9600 bps
                    MNP-Compatible, 2400 or 1200 bps
                    Non-MNP Compatible, 2400, 1200, 300 bps
               Flow Control
               Maximum Throughput
               High-Speed Channel Turnaround
               Link Negotiation
               Data Rate Defaults

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               Nonvolatile Memory (NRAM)
               Phone Number Storage
               Dialing Stored Numbers
               Busy Answer
               Inactivity Timer
               














































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          CHAPTER 4 -- Interface Controls                     4-1

               Terminology
               Throughput Guidelines
               Error Control
                    ARQ Retry Timeout
                    Online Data Rate Fallback
                    Error Control Modes (&Mn)
                         With Auto Answer
                    Data Compression Mode (&Kn)
               Flow Control
                    Transmit Data Flow Control (&Hn)
                         Hardware Control
                         Software Control
                    Received Data Flow Control
                         Hardware Control (Rn)
                         Software Control (&In)
               Data Rate Commands
                    Variable Rates
                    Fixed Rates
                    Maximum Throughput Settings
                    DTE Rate Select (&Bn)
                    Link Rate Select (&Nn)
               DSR Override (&Sn)
               
          CHAPTER 5 -- Internal Controls                    5-1

               Setting/Using Defaults
                    Writing Defaults to NRAM (&W)
                    Loading the Factory Defaults (&F)
                    Resetting to NRAM Defaults (Z)
                    Storing Telephone Numbers (&Zn=s)
               Result Codes
                    Response Modes (Vn)
                    Result Code Sets (Xn)
                    Quiet Mode (Qn)
                    /ARQ Result Codes
               Local Echo
                    Command Mode Local Echo (En)
                    Online Local Echo (Fn)
               The Audio Monitor
                    Speaker Control (Mn)
               Modem Clock Usage (Kn)
               Transmitter Enable/Disable (Cn)
               Break Handling (&Yn)
               The S-Registers
               





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          CHAPTER 6 -- Dialing and Answering                6-1

               Basic Requirements  
                    Transmission Rate   
                    Error Control  
                    Automatic Retrain   
               Placing Calls  
                    Dial Command (D)    
                    Dialing Type, X0 or X1 Setting     
                    Adaptive Dialing, X2-X6 Settings   
                    Pause (,) 
                    Dial and Return to Command Mode (;)     
                    Dialing Letters (") 
                    Transferring Calls (!)   
                    Wait for a Second Dial Tone (W)    
                    Wait for an Answer (@)   
                    Reversing Originate/Answer Frequencies (R)   
               Canceling Dialing (any key)   
               Redialing 
                    Re-execute the Last Command (A/)   
                    Automated Redialing (>, A>)   
                    Continuous Repeat (>)    
                    Continuous Re-Execute (A>)    
                    Exiting Repeat Mode 
               Dialing a Stored Number (DSn) 
               Escape Code Operations (+++)  
                    Modem Response to +++
               Returning Online (O)     
               Hanging Up (Hn)     
               Automatic Answering 
                    Suppressing Auto Answer  
                    Points to Remember
               International Calls 
                    U.S./CCITT Answer Tone (Bn)   
                    Guard Tone (&Gn)    
                    Pulse Dial Make/Break Ratio (&Pn)  
          
          Chapter 7--Queries and Help Screens               7-1
          
               User Inquiries (In) 
               S-Register Query (Sr?)
                    S17
                    S20
               Phone Number Query (&Zn?)     
               Help Screens   
                    Basic Command Set ($)    
                    Extended Command Set (&$)     
                    Dialing (D$)   
                    S-Register Functions (S$)     
          


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                              PART II.  REFERENCE

          Appendix A--Error/Flow Control Concepts
               MNP Level Negotiation
                    Throughput
                    Level 1
                    Level 2
                    Level 3
                    Level 4
                    Level 5
               Error Detection/Retransmission
               Flow Control
                    Example 1--Transmit Data
                    Example 2--Received Data
          
          Appendix B--Summaries and Tables             B-1
          
               The RS-232C Interface, with Pin Definitions
               Front End Indicators
               DIP Switch Summary
               Default Settings
               S-Register Summary
               ASCII Chart
          
          Appendix C--Alphabetical Command Summary     C-1
          
          Appendix D--Problems and Solutions           D-1
          
               If You Still Have Problems
          
          Appendix E--Additional Operational Information    E-1
          
               Using Both Voice and Data Communications
               High Speed/Low Speed Protocol 
               Retrain Sequence
               PBX, Dedicated Line, and Leased Line Operations
               Hewlett Packard Installations
               Analog Loopback and Other Tests
          
          Appendix F--Technical Specifications              F-1
          
          Glossary                                          G-1
          
          Index








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                                                                COURIER HST


          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, and 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 at 800/982-5151 (in Illinois,
          312/982-5151), or by mail at 8100 North McCormick Blvd., Skokie,
          Illinois, 60076.  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.

          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.









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                              FCC REGISTRATION NUMBERS

                              FCC68:  CJE794-11323-DM-E
                              RINGER EQUIVALENCE:  0.4B
                                 FCC15:  CJE794FAST
                                          
                                          
          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, USRobotics,
          Inc., 800/982-5151 (in Illinois, 312/982-5151).

          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.  The Courier HST has been tested and found
          to comply with the limits for a Class B computing device in
          accordance with the specifications in Subpart J of 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:

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                                                                COURIER HST


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















































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                                                                COURIER HST


          
          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 HST Modem Load Number:  38B

          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.  An alphabetic suffix is also specified
          in the Load Number for the appropriate ringing type (A or B), if
          applicable.  For example, LN = 38B designates a Load Number of 38
          and a B-type ringer.







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          HOW TO USE THIS MANUAL

          This manual is divided into two parts.  The first part is
          designed to aid you in getting your modem connected and operating
          as quickly as possible.  Part I also includes chapters on command
          usage.  Part II contains a number of informative appendixes that
          you may or may not need, depending on your situation, plus a
          Glossary and Index.

          Below is a brief description of the manual's contents.  We
          suggest you review at least Chapters 1-3 before operating the
          modem.

               o    Chapter 1 -- Introduction

               o    Chapter 2 -- Assembling and testing the modem

               o    Chapter 3 -- Immediate operations -- essentials

               o    Chapter 4 -- Interface controls

               o    Chapter 5 -- Internal controls

               o    Chapter 6 -- Calling, answering and disconnecting

               o    Chapter 7 -- Inquiries and Help screens

          The appendixes in Part II cover the following subjects:

               o    Background information on error and flow control

               o    Summaries and tables

               o    Problems, their causes, and solutions

               o    Additional operational information

               o    Technical specifications













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