Carrier Detect 7-3
Carrier Detect Carrier means there is communication with the device on the other end
of the connection. Under normal conditions, the Business Modem sends
a Carrier Detect (CD) signal in response to establishing a connection with
another modem. You can use the AT&Cn command to control how the
Business Modem sends the CD signal.
.
For your modem to Command
Have CD always ON. AT&C0
Send CD normally (the Business Modem sends a CD signal
when it connects with another device, and drops the CD signal
when it disconnects).
AT&C1