| 摘要 |
PROBLEM TO BE SOLVED: To provide an interphone system that can inform a visitor of the response of a resident indoor. SOLUTION: When a visitor depresses a call button 36 of an entrance slave unit 2, a call detection circuit 15 of a master unit 1 detects a fact of the depression, and a speaker 13 sounds a call tone. When a resident replies by using a microphone 11 or the like of the master unit 1, an FM modulation circuit 12 generates a carrier signal that is frequency-modulated, the carrier signal is sent to an FM demodulation circuit 22 and a detection circuit 25 of the entrance slave unit 2 via a transmission line 3, and when the detection circuit 25 detects the carrier signal frequency-modulated by a voice signal, the circuit 25 outputs a lighting signal (c) to turn on reply confirmation light of the entrance slave unit 2.
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