| 摘要 |
PURPOSE:To attain optionally communication among three stations of a slave set, a master set and a sub-master set by superimposing a signal having a sufficiently lower frequency than that of a voice signal onto the voice in case of communication between the master set and the sub-master set. CONSTITUTION:In calling the sub-master set from the master set, the talking between the master set and the slave set 1 is disconnected. Then a control circuit 8 operates a modulation circuit 9, a tone squelch circuit 7, an automatic gain adjuster 11, a receiver amplifier 10, a demodulation circuit 6 and an input/output circuit 5. A low frequency signal sufficiently lower than the frequency of the voice is outputted from the control circuit 8, the signal is frequency-modulated by the modulation circuit 9, fed to the input/output circuit 5 and outputted to a power line. The sub-master set uses the input/output circuit so as to receive the signal from the master set and demodulate it by the demodulation circuit. When the tone squelch circuit detects the low frequency signal, a call tone is outputted from the control circuit 8. |
