FaxModem/V.42bis  (250-3028)      Troubleshooting      Faxback Doc. # 3293

Following are the most common causes for 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 modem that your're
    calling.  You should normally use 8 data 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 your modem set at 300 or 1200 bps you will not be able
    to communicate.  However, you'll find that most bulletin boards and
    other services will adjust to the speed of the calling modem.

4.  Your communications software has not been set up properly.  Re-check
    the Initialization String and Dial String.

5.  Your modem works fine when you're not using compression, but the
    compression (V.42bis and MNP5) features are inoperative.  Check to be
    sure that the cable you are using supports hardware flow control.  If
    you have a Mac, make sure that your cable is wired correctly.  The Mac
    128 and 512 do not support hardware flow control.

6.  Your software requires that your modem IGNORE DTR (the Hayes default
    setting), and the non-volatile memory is set so that the modem will
    follow DTR.  If so, change the setting by using the following command:

        AT&DO&WO&YO

7.  Your software requires that DCD is always forced ON (the Hayes default
    setting), and the non-volatile memory is set so that DCD follows
    carrier.  If so, change the setting by using the following command:

        AT&CO&WO&YO

8.  Your modem's power-on set-up is not what your communications software
    wants.  Be sure you know what setting the software wants.

9.  You are communicating in or to 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.

(br/all-11/3/94)