| 摘要 |
PURPOSE:To perform a direct channel selection among stations with no intervention of a master device, by selecting a channel selection control signal with a channel selection switch, and detecting the channel selection control signal through a connecting circuit of a station to be called for connection of a talking circuit. CONSTITUTION:A transmission line L1 for control signal is provided along with a transmission line L2 for audio signal. Both a connecting circuit 1 and a talking circuit 2 are provided at each of plural interphone stations I1, I2... and doorphone stations D1, D2.... The control input/output of the circuit 1 is connected to the line L1, and the call input/output is connected to the line L2. An optional calling station sets a poper station to be called by means of a channel selection switch provided at the circuit 2 to select the channel selection control signal via the line L1 and at the same time connects the circuit 2 of own station to the line L2. The called station detects the channel selection control signal through the circuit 1 and connects the circuit 2 of own station to the line L2. |
