If  you haven't change any other software or  hardware  then
the  modem probably needs repair. Call 617-423-1072 for  Customer
Service.   If there has been any software or hardware  additions,
one of them may be causing a conflict.

    (External)->  When you try the dos software (which is  what?)
does  the  TR  led  come on? If not,  then  the  comport  is  not
contacting  the modem at all. Do the RD/SD leds blinks  when  you
send commands to the modem? If they both blink then the modem  is
echoing  commands.  If  only one blinks then  the  modem  is  not
echoing commands.
     (Both)  -> Can you type AT and get an OK reply? If not  then
the   modem   (Ext  -  if  RD/SD  blink)  is  echoing   but   the
serial/computer  may not receive /display the echo.  (Both)->  If
all else fails, try ATA and see if you hear the modem pick up the
telephone  line and start squealing. If so, (Ext - and the  SD/RD
leds  blink,)  the modem probably is OK and there is  a  computer
hardware conflict (modem, mouse, scanner and so forth).