Communications management system having multiple power control modes

A communications management system for use in conjunction with a host computer includes independently powered processing circuitry which automatically powers up the host computer upon receipt of an incoming message or initiation of an outgoing message, thereby avoiding the need for the computer to be continuously powered. The computer is also powered-up by user-actuation of a panel switch, or by an internal timer which establishes a predetermined powered-up monitoring period. A mode selection circuit prevents conflicts between the various power control factors when powering down the computer.