                              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 data over the
      phone link.
      
Before the Modems Connect

Your modem . . .
   Doesn't answer the phone or go off hook to
   dial a number
      Review the quick configuration guide or
      your software manual to see what Data
      Terminal Ready (DTR) operations your
      software requires.  Then check to see if
      DIP switch 1 is set correctly.
   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.Make sure your computer is in
         Terminal mode.  This is a
         communications software function.
         See Testing the Installation in
         Chapter 2.
      3.Check to see that your 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).
         Also make sure your software is set
         to the correct communications
         (serial) port, as determined in the
         setup instructions in Chapter 2,
         under Selecting a Serial Port.
      4.Check that DIP switch 8 is DOWN, for
         command set recognition.  If the
         switch is UP, set it DOWN and 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 result codes)
        ATV1 <Enter> (to display verbal result
                     codes)
      6.Review the quick configuration 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.
   Displays double characters
      Both your modem 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
      Review the quick configuration guide
      that came with the modem or your
      communications software manual to see
      what Carrier Detect (CD) operations are
      required.  Then check to see if DIP
      switch 6 is set correctly.
   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 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
         you are in the correct mode for the
         call you are receiving.  The modem
         must be in data mode to receive a
         data call, and in fax mode to receive
         a fax call.  See Fax Operations in
         Appendix E for information on
         switching between fax and data modes.
      2.Check to make sure that you've set
         your software to the same word
         length, parity and number of Stop
         bits required by the remote computer
         and, if your modem is dialing out,
         that your software is set to a bit
         (or baud) rate equal to or higher
         than that of the remote modem.
      3.Make sure the modem at the other end
         of the line is V.32 bis-compatible at
         14.4K, 12K, 9600, 7200 or 4800 bps,
         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.
      4.Make sure your modem's link rate
         setting, &Nn, is correct for the
         call.  If the link rate is locked at
         a speed (&N1O&N8) different from the
         calling modem's, the Sportster hangs
         up.  The factory setting of &N0,
         variable link operations, allows the
         two modems to negotiate the highest
         possible link rate.
         
      5.If these steps fail to 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 an
         other 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 your
      communications software is set to the
      same bit rate (or higher) as that of the
      remote modem, and that both your
      software and the remote system are set
      to the same 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.Place the call again.  The phone
         company routes even local calls
         differently each time you call.
      2.Call 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 your
      communications software is set to the
      same bit rate (or higher) as that of the
      remote modem, and that both your
      software and the remote system are set
      to the same word length, parity and
      number of Stop bits.  If the settings
      are correct, the problem may be with the
      phone line.
      If the modem is set to a fixed serial
      port rate (&B1) and your software is
      fixed at 19.2K, 38.4K, or 57.6K bps, the
      reason may be one of the following.
      1.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.
      2.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 computer is also echoing.
      There are two ways to handle this:  one
      is to terminate the call, hang up, turn
      off the online echo (ATF1) when the
      modem is in Command mode, and call
      again.  This way you will not lose any
      data.  The second, riskier way is to
      force the modem into Online-Command mode
      by sending the escape code and to send
      the modem the ATF1 O command.  The
      command turns off the online echo and
      returns the modem online.  Use this
      second method only if the remote system
      and your modem are not in the middle of
      data transfer.
      
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 Our Service Representatives
         will be happy to give you assistance
         over the phone Monday through Friday
         from 7:30 a.m. to 6 p.m. (Central
         Time Zone).  If you prefer, you can
         contact us by fax at 708-982-0823.
      4.If it is necessary to return the
         modem for service, the Service
         Representative you talk to will give
         you a Return Materials Authorization
         (RMA) number.
        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 card
           board 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.  Modems
           without an RMA number will not be
           accepted.
         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 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.

