| 摘要 |
PROBLEM TO BE SOLVED: To provide a relay interphone master set, where possibility of malfunctions is precluded, in the case of monitoring a camera slave set of an interphone master set. SOLUTION: A transmission signal processing means 10 is provided with a demodulator 10a that receives a modulated carrier to extract a control signal, an amplifier circuit 10b that amplifies the output from the demodulation 10a, a signal processing circuit that has an input port P to receive the amplified signal from this amplifier circuit 10b, compares the control signal with a predetermined reference pattern, so as to discriminate the control signal and to conduct required signal processing, and a carrier control means 10c that activates the amplifier circuit 10b, when the demodulator 10a receives the modulated carrier on one hand and interrupts power to the amplifier circuit 10b when receiving no modulated carrier on the other hand.
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