INTERCOM SYSTEM, LIVING ROOM SIDE REPEATER, AND LIVING ROOM MASTER UNIT

摘要

PROBLEM TO BE SOLVED: To prevent unwanted noise being outputted from a modulation circuit for transmitting voice signal from flowing to a transmission line in an intercom system for transmitting voice signal and a control signal by utilizing the transmission line of a private CATV system configured in a collective housing.;SOLUTION: A voice signal for conversation outputted from a living room master unit 26 is FM modulated at an FM voice modulating section 51 and transmitted on the transmission line of a private CATV system. The FM voice signal transmitted from a collective entrance facility through the transmission line is demodulated at an FM voice demodulating section 60 and outputted to the living room master unit 26, and an FM video signal superimposed with a DC power supply is outputted to a monitor 27. In such a dwelling unit adapter 21, a current detection circuit 55 detects conversation operation of the living room master unit 26 from a current flowing through the transmission line of DC power supply and supplies power to the FM voice modulating section 51 and the FM voice demodulating section 60 only during conversation operation of the living room master unit 26.;COPYRIGHT: (C)2006,JPO&NCIPI