7CONTROLLING EIA-232
SIGNALING
This chapter contains information about configuring the EIA-2321
signalling between your computer and modem:
■Data Terminal Ready
■Data Set Ready
■Carrier Detect
Data Terminal
Ready Your computer sends a Data Terminal Ready (DTR) signal to the Business
Modem when it is ready to send and receive data. The &Dn command
tells the modem how to respond to the DTR signal.
Example: Sending AT&D1 before connecting with another device,
dropping DTR will enter Command Mode.
1.The EIA-232 Standard was formerly known as RS-232 (RS stands for
Recommended Standard).
For your modem to Command
Ignore the state of DTR and act as if DTR is always present. Use
this command with equipment that cannot provide DTR. AT&D0
If issued before connecting with another device, enter online
Command Mode during a call by dropping DTR. Most
communications software packages have a method for
toggling DTR. Refer to your software’s manual for details.
AT&D1
Respond normally to the DTR signal.
The Business Modem will not accept commands until your
computer sends a DTR signal. The call will end when the DTR
signal is dropped.To change the DTR recognitio n t ime, set
S-Register 25. See Appendix A, S-Registers for more
information.
AT&D2
Business Modem hangs up and resets upon loss of DTR signal. AT&D3