| 摘要 |
PURPOSE:To adjust brightness automatically corresponding to the intensity of incident light by outputting a signal from a pulse generation part when an illuminance detecting circuit outputs an electric signal, and making a light emitting element illuminate with the brightness of DC pulses. CONSTITUTION:A photodiode 10 outputs an electric signal corresponding to the quantity of photodetection. An amplification part outputs an amplified output voltage and then a V/F converter 12 generates reference pulses of frequency corresponding to the voltage and outputs them to a main pulse generation part 13 and a slave pulse generation part 14. When the reference signal is inputted, the main pulse generation part 13 generates a main pulse signal and outputs it to the base of a 1st transistor(TR) 15. At the same time, the slave pulse generation part 14 generates and outputs a slave pulse signal to the base of a 2nd TR 16. Therefore, when a self-illumination type push button 3 is pressed, only a DC pulse based upon the pulse width and frequency of the main pulse signal is applied to the light emitting diode 3bb of the self- illumination type push button 3 and the brightness of the light emitting diode 3bb becomes maximum. A current flows to the 2nd TR 16 unless the self-illumination type push button 3 is pressed, and the brightness of the diode 3dd becomes about a half as large as that when the self-illumination type push button 3 is pressed.
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