| 摘要 |
PURPOSE:To prevent the exhaustion of a power source by providing a timer circuit which is driven by the detection signal of a signal decision circuit, and maintains the output pulse of a control pulse generation circuit extending over prescribed time, and restricting the power source so as to be consumed mainly only during pulse outputting time by the control pulse generation circuit. CONSTITUTION:The signal decision circuit 3 is driven by the output pulse of the control pulse generation circuit 1 extending over the pulse width of it, and detects whether a prescribed signal is received or not during the said time. When it detects that the prescribed signal is received, it outputs the signal S3, and drives the timer circuit 4. The timer circuit 4 maintains the pulse to be outputted by control pulse generation circuit 1 extending over the prescribed time based on the output signal of the signal decision circuit 3. On the other hand, the said timer circuit 4 closes a switching circuit 5 by its output signal S4, and supplies a power source S5 to a sound amplification circuit 6, and comes ready for reception. Accordingly, the consumption of the power source at the time of a waiting reception can be widely prevented.
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