| 摘要 |
PROBLEM TO BE SOLVED: To provide a solar battery type signboard allowing a solar battery and a storage battery to do with smaller capacity. SOLUTION: A normally-open switch 7 is arranged in the line connecting between a storage battery 3 and an electric display board 4, and the switch 7 is controlled on-off by a noise discrimination circuit 6 with a microphone 5. When a train is approaching to the electric display board 4 at night, the noise of the train is taken in the noise discrimination circuit 6 via the microphone 5, and when this detection signal satisfies prescribed conditions, the noise discrimination circuit 6 makes the switch 7 on to turn on the electric display board 4. Then, when the train goes away, the switch 7 is brought into off-state to turn off the electric display board 4. In such a manner, it is possible to avoid wasting unnecessary power consumption of the signboard during the night, and reduce capacities of the solar battery and storage battery compared with those of conventional ones.
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