| 摘要 |
PURPOSE:To avoid power consumption at no sound and to save useless power consumption, by recording high frequency signal on an endless tape and interrupting the power supply to an audio signal amplifier through the detection of a detector. CONSTITUTION:In the device repetitively broadcasting the audio signal recorded on an endless tape of a dam discharge system, a high frequency signal is recorded before the recording of audio signal. When a control signal is input to a control device 2 of a broadcast device, a start switch ST is on to operate the hold switch-on. Thus, power supply is fed to a playback device 1 to activate it, and the output signal is input to HPF and LPF of the circuit 2. At first, audio signal is played back and broadcast is made from a speaker 4 via LPF and amplifier 3. When the broadcast is finished, the high frequency signal is reproduced to operate a relay SIG via HPF, delay circuit DEL, and detector DET and to cut off the power supply to the amplifier 3. When the high frequency signal is absent, the relay SIG is restored to turn off the switch-on and the supply of power to the playback device 1 is stopped. |
