| 摘要 |
PURPOSE:To eliminate the influence based on the malfunction of the decoder, by introducing a timer between the switch circuit and the decoder and by restraining the time of conduction of the switch circuit within a fixed time. CONSTITUTION:If the start code of the emergency broadcast is detected by decoder 3, the output signal operates timer 8, and the signal to make switch circuit 4 conductive is generated in the output only during a time determined preliminarily. If the end code of the emergency broadcast is detected within this time by decoder 3, this signal is applied to the reset terminal of timer 8, and the operation of timer 8 is stopped. When the duration of the emergency broadcast is longer than the operation time of timer 8 and the emergency broadcast cannot be heard from speaker 6 on the way of the broadcast, switch 9 is operated manually to supply power. |
