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          APPENDIX D
          PROBLEMS AND SOLUTIONS
          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.

          -----------------------------------------------------------------
          PROBLEM                  SUGGESTED SOLUTION
          -----------------------------------------------------------------
          Before Establishment of the Data Link
          -----------------------------------------------------------------
          
          Your modem . . .

          Doesn't answer the phone or go "off hook" to dial a number

          Check to make sure your computer or terminal is sending a Data
          Terminal Ready (DTR) signal via the RS-232C interface.  See
          Appendix B-1 and Appendix B-3, DIP switch 1.

          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.

          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 3 is DOWN, for result code display,
               and that DIP switch 2 is UP, for verbal result codes.  If
               not, change the switch(es) and issue ATZ <cr>.  Or issue
               whichever of these commands is needed:

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

          5.   Your machine may require the Carrier Detect override (DIP
               Switch 6 DOWN), but you've changed the factory setting.
               Check Appendix B-3.

          6.   A rare condition is that your terminal/computer reverses the
               send/receive functions at the RS-232C interface.  See
               Appendix B-1, Appendix B-3, Quad switch, and your equipment
               documentation.

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          -----------------------------------------------------------------
          PROBLEM                  SUGGESTED SOLUTION
          -----------------------------------------------------------------
          Before Establishment of the Data Link
          -------------------------------------

          Your computer . . .

          Reacts as though a data link has been established, but no call
          has been received

          DIP Switch 6 is set DOWN at the factory for Carrier Detect
          override, but your system may be reacting to improper signals
          received at the RS-232C interface.  Set DIP switch 6 UP (OFF).

          When the modem is in Answer Mode, acts as if 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.  Entering the Quiet Mode
          command, ATQ1 <cr>, should solve the problem.

          Both modems . . .

          Exchange carrier signals, but fail to establish a communications
          link

          1.   Check to make sure the proper bit rate, word length, parity
               and number of Stop bits have been selected.

          2.   If that doesn't correct 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.

          3.   Make sure the modem at the other end of the line is USR-HST
               compatible at 9600 bps, V.22bis-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.

          -----------------------------------------------------------------
          PROBLEM                  SUGGESTED SOLUTION
          -----------------------------------------------------------------


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          During Data Transfer
          -----------------------------------------------------------------

          Your screen displays . . .

          Only brackets

          Check to make sure both modems are at 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.  (However, if it does, the problem may still be
               with the phone line.)

          3.   If you are using a long-distance service and the problem
               persists, you might try using a different service.

          Random (garbage) characters

          Make sure both modems are set at the same bit rate, word length,
          parity, and number of Stop bits.

          Double characters

          The modem's online local echo is probably ON.  Return the modem
          to Command Mode (use +++) when it's convenient, and then type:

                    ATF1 <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
               USRobotics.



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          3.   If your dealer can't clear up your difficulties, call the
               USRobotics Technical Support Department at 800/982-5151 (in
               Illinois, 312/982-5151).  Our Service Representatives will
               be happy to give you assistance over the phone Monday
               through Friday from 8:30 a.m. to 5 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 follow this
               procedure --

               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
                         USRobotics, Inc.
                         8100 North McCormick Boulevard
                         Skokie, Illinois 60076

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

               e.   USRobotics will repair your modem and return it to you
                    via United Parcel Service.

          















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