| 摘要 |
PURPOSE:To attain bidirectional calling independently of a master or a slave device by setting a receiving circuit to the 1st CH (channel) at standby, setting a transmission circuit to the 1st CH at calling, the receiving circuit to the 2nd CH, and setting the transmission circuit to the 2nd CH and the receiving circuit to the 1st CH at incoming call. CONSTITUTION:Plural interphones 6 are connected to an AC line 2. A transmission circuit 10 consists of a transmitter 11, FM modulating circuit 13, and amplifiers 12, 14. A receiving circuit 20 consists of a BPF21, FM demodulating circuit 23 and a receiver 25. A control circuit 30 consists of a CPU31, ports 34-38, and a hook switch 42. The circuit 20 is set to A-CH at standby. The circuit 13 is set to the A-CH by the CPU31 at dialing and the BPF21 is set to a D-CH. Further, the circuit 13 is set to the D-CH and the BPF21 is set to the A-CH at incoming call. |
