           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.


Before Establishment of the Data Link             


Your modem . . .

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

      Review the Settings Supplement 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.

   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 DOWN, for
         command set recognition.  If the
         switch is UP, power off the modem,
         set the switch DOWN, and power on the
         modem again.  Try typing AT <Enter>
         again.

      5. 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 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 Settings Supplement that
         came with the modem or your communi-
         cations 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 Appendix B-1,
         Appendix B-3, Quad switch, and your
         equipment documentation.

   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 DOWN 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
      Settings Supplement 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, acts 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.
      Sending the Quiet Mode command, ATQ1
      <Enter>, should solve the problem.
Both modems . . .

   Exchange carrier signals, but fail to
   establish a communications link

      1. 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 Chapter 7. 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.

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

      3. 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.

      4. Depending on your model, make sure
         the modem at the other end of the
         line is HST compatible, V.32 bis
         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.

      5. 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.

   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 DTE rate
      (&B1) and your software is fixed at
      19.2K or 38.4K 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 bis
         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 dis-
         able the kind you are not using.
   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 UP (factory setting),
      the modem hangs up when it returns to
      Command mode, and you'll have to call
      again.  If DIP switch 9 is DOWN, 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
         USRobotics.

      3. If your dealer can't clear up your
         difficulties, call the USRobotics
         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 7:30 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
         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.
