User`s guide

AT Commands
5-20 Modem 3600
Data Set Ready &S
These commands control the DSR signal generated by the modem to
indicate that the modem is ready for operation. DSR must be on for
some terminals and devices to communicate with the modem.
Data Terminal Ready &D
In data mode DTR may be used for modem control.
Note
If DTR controls dialer is selected, selecting DTR active will
cause an autodial after an off-to-on transition of DTR.
Command Operation
&S DSR always on
&S1 DSR on when off hook in data mode
&S2 DSR off for 5 seconds after disconnect then returns
to on
&S3 DSR follows off hook (OH) signal
Command Operation
&D The modem ignores DTR.
&D1 The modem goes to command mode from data
mode when DTR goes from on to off.
&D2 Disconnects when DTR goes from on to off;
disables autoanswer while DTR is off.
&D3 Disconnects, recalls command mode, and resets the
modem to a stored configuration when DTR goes
from on to off.
In dial line mode the modem disconnects; in leased
line, the modem retrains.