carrier
The carrier option allows Autolog to monitor the carrier detect,
or DCD, signal from your modem. If carrier is lost while in talk
mode, Autolog will return you to command mode.
If a file transfer was in progress, it will be
aborted. Turn the carrier option on or off with the command:
carrier true or false
The carrier option requires that your modem, cable, and communications
port all provide the carrier detect hardware signal, used to indicate when
a connection with another modem is present and when a connection is terminated.