2400 BPS Pocket FaxModem  (250-3105)  Troubleshooting  Faxback Doc. # 2798

The following are the most common causes of error:

1)  If all the characters that you type appear twice on the screen, your
    communications software may be set for "half duplex" when it should be
    set for "full duplex".  This can be corrected by using your
    communications software configuration menu to change from half to full
    duplex.

2)  Your software's selection of the number of data bits, the parity, and
    the number of stop bits is different from the faxmodem that you're
    calling.  You should normally use 8 bits, NO parity, and 1 stop bit
    (8,NONE,1).  The second most common setting is 7 data bits, EVEN
    parity, and 1 stop bit (7,EVEN,1).  If you call another modem and
    connect, but get incomprehensible characters displayed (even after
    some normal connection noise), try changing these settings.

3)  You are calling a modem set up for one speed, and you are at a
    different speed.  Some 2400 bps information services have dedicated
    lines that can only communicate at 2400 bps.  Therefore, if you call
    them with a 300 or 1200 bps modem speed, you will not be able to
    communicate. On the other hand, many bulletin boards and other
    services will adjust to the speed of the calling faxmodem.

4)  Your communications software has not been setup properly.  Recheck
    the initialization string and dial string specified in your software
    manual and in "Setting Up Your Modem Communications Software".
    Remember that commands in the initialization string are sent to the
    faxmodem each time you start your software & will override settings
    stored in the faxmodem's non-volatile memory.  Many communications
    program for PC-compatible computers require that the faxmodem be
    configured using &C1 and &D2, using either the faxmodem's non-volatile
    memory or the software's "modem initialization string".  Also, read
    the discussion about turning off hardware flow control on page 13.

5)  You are turning your faxmodem on after you start up your software.
    This can cause a problem because most programs will send an
    initialization string to the faxmodem when the software starts up.
    If the faxmodem is off at that time, it will not receive the
    initialization string.  Solution: Turn on your faxmodem, then start
    up your software.

6)  If your software requires that your faxmodem ignore DTR (which is the
    faxmodem's default setting) and you are using the &D2 command in the
    modem initialization string or have stored it in non-volatile memory,
    your faxmodem will not work properly.  If this is the case, store the
    &D0 command in non-volatile memory:

          AT&D0&W0&Y0

Also, make sure that the modem initialization string does not contain &D2.

Conversely, if your software requires that your faxmodem follow Data
Terminal Ready, the above considerations apply in reverse.  If you are
having problems, include &D2 in the modem initialization string.  Most
software for IBM-compatible (but not Macintosh) computers requires the
use of &D2.

NOTE: If you are using a Macintosh, you may not be able to receive calls
      if &D2 has bee saved in non-volatile memory or if it appears in the
      initialization string.  Use the faxmodem's default setting, &D0,
      instead.

7)  If your software requires that DCD always be forced ON (which is the
    modem's default setting), and you are using the &C1 command in the
    modem initialization string or have stored it in non-volatile memory,
    your faxmodem will not work properly.  If this is the case, store the
    &C0 command in non-volatile memory:

          AT&C0&W0&Y0

Also, make sure that the modem initialization string does not contain &D2.

Conversely, if your software requires that Data Carrier Detect follow
carrier, the above considerations apply in reverse.  If you are having
problems, include &C1 in the modem initialization string.  Most software
for IBM-compatible (but not Macintosh) computers requires the use of &C1.

8)  Your faxmodem's power-on setup is not what your software
    communications software wants.  Be sure you know what setting the
    software wants and re-read "Using Non-volatile Memory Instead of DIP
    Switches for Power-up Configuration".  In general, you can use the
    software's modem initialization string to solve this type of problem.

9)  You are communicating in or with an area outside the USA where you
    need to generate a special tone called a "guard tone" to disable echo
    suppressors.  Guard tones are set with the &G command, as discussed in
    the Command Set chapter, under AT Commands.

10)  You have a Macintosh, and the "A" in "AT" commands does not always
     appear on the screen.  When the faxmodem is coming out of the sleep
     mode and is connected to a Macintosh, the first character sent to the
     Macintosh will not appear on your computer, but is sent to the
     faxmodem, which will respond appropriately.  There is, therefore,
     no problem.

11)  Your faxmodem works as a faxmodem but will not fax.  Make sure that
     your fax software is intended for use with Class 1 faxmodems.  If you
     are using a Macintosh, make sure that you have the right cable.  See
     Appendix C.

(smc-12/20/93)
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