Data Line Monitoring - Tandy DCM-7 Operation Manual

Hayes protocol reference
Data line monitoring
The DCM-7 can be used to monitor a data line up to 300 bps as shown in
the figure below. To accomplish this monitoring
mod~;
the Modem's carrier
transmitter should be turned off and loss of carrier condition should be
ignored.
"For originate mode, input:
AT CO 810
=
255 D (ENTER)
For answer mode, input:
AT CO $10
=
255 A (ENTER)
Computer
Terminal
300 bps
modem
DCM-7
Computer
48