INTERPHONE WITH BIDIRECTIONAL VIDEO MONITOR

PURPOSE:To enable even a visitor to check an interior condition With a monitor television by providing a monitor camera in a room and the monitor television outdoors, modulating the video signal from the monitor camera in the room, transmitting this signal to the outdoor monitor camera and demodulating the signal on the outdoor monitor camera side. CONSTITUTION:A slave machine is short-circuited in a lower resistance and the voltage of a video signal line L drops when the visitor operates the call button of the slave machine. This voltage drop is detected on a master machine side and calling sounds are produced or a power source is supplied to the slave machine. The monitor cameras B, C are simultaneously driven and the bidirectional video signals are projected on both monitor televisions A, E of the master machine and the slave machine by modulation and demodulation. The communication and video transmission are ended by placing the hand set of the master machine.