VIDEO INTERPHONE SYSTEM

摘要

PROBLEM TO BE SOLVED: To extend a master set to a system consisting of a master set and a slave set with a simple configuration. SOLUTION: A relay master set 3 of this video interphone system is provided with a demodulation circuit 32 that demodulates a signal received from a master set 1 and a changeover means 41 that applies switching control of connection between the master set 1 and a slave set 2. The master set 1 uses a voice modulation circuit 15 to modulate a control signals and transmits the modulated control signal and when the master set 1 detects interruption from the slave set 2 by the changeover means 41 through an increased voltage, the master set 1 erases a video image displayed on a monitor television receiver. When the relay master set 3 uses a demodulation circuit 32 to detect the control signal from the master set 1, the relay master set 3 erases a video image displayed on the monitor television receiver and allows the changeover means 41 to interrupt the connection between the master set 1 and the slave set 2 when starting a speech.