| 摘要 |
PURPOSE:To provide information with an alarm output when visibility is lowered by re-ceiving a light outputted from a light emitting device with a photoelectric conversion circuit and constituting the device so that an alarm signal is sent when the output signal becomes a prescribed level or below. CONSTITUTION:The photoelectric conversion circuit 10 receives environmental light 15 or the light emission output 13 of the light emitting device 12, and supplies an illuminance signal 18 to a monitor circuit 16 and a control part 17. The light emitting device 12 is constituted so as to emits the fixed light emission output 13 to the photoelectric conversion circuit 10, and is constituted of e.g. an LED. Since the LED whose light emission output is in proportion to a current flowing through there and in inverse proportion to an ambient temp. as the characteristic, the fixed light emission output is obtained. The monitor circuit 16 outputs the alarm signal to an alarm 22 through a transmission line 21 when the level of the illuminance signal 18 received from the photoelectric conversion circuit 10 becomes a fixed value or below when the circuit 16 receives a light emission command signal 19 from the control part 17.
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