| 摘要 |
PROBLEM TO BE SOLVED: To provide an interphone system that can supply power to a transmission circuit of a doorphone salve unit only at, call times between an interphone master unit and the doorphone slave unit. SOLUTION: The interphone system is provided with the interphone master unit 1, that is installed in a house and the doorphone slave unit 2 connected to the interphone master unit. The interphone master unit is provided with a power supply circuit 13, that applies a call detection system voltage to the doorphone slave unit, when the interphone master unit is in a standby state and detects a call, a speech system power supply circuit 17 that applies a speech system voltage different from the call detection system voltage to the doorphone slave unit in the case of a call, and a call detection circuit/speech circuit changeover section 15 that selects the circuits 13 and 17 to connect them to the doorphone slave unit. The doorphone slave unit uses a voltage detection circuit 27 that detects the voltage supplied from the interphone master unit for supply the speech system voltage to a transmission circuit 28 when detecting the speech system voltage. |
