Multitech MMH900 User Manual page 163

Appendix J - Internal MMH2834 Composite Link Modem Commands
RETURN. Do not include the letter D in this command, or the
stored number will be erased (also see Section J.1.3., on Phone
Number Memory Commands).
DTR An alternate method of causing the MMH2834 to
Dialing automatically dial is DTR Dialing. Data Terminal Ready (DTR)
is a signal that comes into the modem from the
$D terminal or computer to which it is connected, on pin 20 of the
RS232C interface. In DTR dialing, the modem automatically
dials a stored number as soon as it receives a high DTR Signal.
The DTR dialing method is popular in synchronous applications.
To activate DTR Dialing, enter AT$D1 and hit RETURN. The
modem dials the phone number stored in the N0 location of
memory when it receives a high DTR signal. DTR must remain
high for the duration of the call, until disconnect. To deactivate
DTR dialing, enter AT$D0 and hit RETURN.
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