To gracefully disable a modem from dialing or answering calls, use the modem busyout command in line configuration mode.
The disabling action is not executed until the active modem returns to an idle state. No active connections are interrupted when you enter this command. If the modem busyout-threshold command is set, this command will be delayed until the DS0 lines to the exchange are taken out of service. For T3 cards the message "No Controller configured" might appear for unconfigured T1 links in the T3.