Subj : SEXPOTS - Pulling my hair out... :)
To   : Digital Man
From : cafarmer
Date : Mon Jun 10 2024 12:26 pm

I tried both AT&C1 (it was a suggested init string for the optima AT&C1&D2) and
ATC1. The modem didn't like AT&C1 - Error.

I cannot find the manual for the HSM 1200. But I did find the manual for the
HSM 300 and a General Smartmodem Guide.

D.5.1 Using the CD line
If you are confident of the communications environment and cabling
requirements, and have access to the RS-232 signal status, then monitoring the
CD line is the easiest carrier loss detection method to implement. This
requires &C1 to be programmed at setup time, or be stored in the modem as the
value recalled on reset or powerup.
However, this is the most restrictive and risky choice. It requires a properly
wired cable and support of &C1 by the modem's command set or proper DIP- switch
settings.

Since there may be some confusion on my part between ATC1 and AT&C1, I'm not
exactly sure if this text applies now:

Cn - Controls 
Smartmodem’s
 transmitter carrier; i.e.,
signal sent
when
 calling, answering or 
connected to a distant modem.
Default C=1
n = 0 Transmitter Off
n = 1 Transmitter On

So this was for the HSM 300 that came before the HSM 1200... I would be
surprised if most of the commands were not supported in the HSM 1200.

ATC1 = OK (not sure what this does. ATC? returns 000)
AT&C1 - ERROR

.