If a port is configured for bidirectional service, the ttymon port monitor does the following:
Allows users to connect to a service.
Allows the uucico, cu, or ct commands to use the port for dialing out, if the port is free.
Waits to read a character before printing a prompt.
Invokes the port's associated service, without sending the prompt message, when a connection is requested, if the connect-on-carrier flag is set.