Intercom system

摘要

The invention is directed to an intercom system for communication between persons on opposite sides of an entry door or the like. On a first embodiment the intercom device is energized by the person on the exterior of the door when a combined power and door buzzer or bell switch is depressed. When energized, voice communication can be established by the combined speaker, microphone and amplifying devices. A sound activated switch positioned on the interior side of the entry door allows hands free communication between the persons on the opposite sides of the door. A timer terminates the system power after a predetermined time span. In a second embodiment, a pair of radio frequency transceivers are employed with the intercom device to allow communication by the person on the interior side of the door who is located remote from the door.