Here are a few settings we have found work with Doom on a modem link.
These were obtained from our modem manuals and we kept the following 
in mind:  Do NOT put in codes that aren't relevant!  iD suggests 9600,
no data compression, and no error correction, and that's it!  Good Luck!


Complete PC Turbomodem Plus
AT&FB8%C0\N1

AT - Hayes Attention Command
&F - Recalls Factory Default
B8 - Sets 9600 bps
%C0 - Turns Off Data Compression
\N1 - Turns Off Error Correction

USR Sportster
AT&K0&M0&N6S27=16
AT - Hayes Attention Command
&K0 - No Data Compression
&M0 - No Error Correction
&N6 - 9600 bps
S27=16 - Disables MNP

Suprafax Modem 14.4
AT&FS37=9
AT - Hayes Command Set
&F - Recalls Factory Default
S37=9 - 9600 bps?