| 摘要 |
PURPOSE:To easily obtain proper contrast at all times by providing a variable resistor for dimmer controlling, enabling the luminance of a vehicle-loaded equipment indicating part to be changed in many stages, and selectably presetting several number of luminances. CONSTITUTION:The captioned circuit, when used in a vehicle-loaded electronic tuning radio receiver consisting of an antenna 1, a high frequency stage 2, a mixer 3, an intermediate frequency stage 4, a detecting circuit 5, a low frequency amplifier 6, and a speaker 7, has a manually operatable variable resistor R1 and an A/D converter 20 which converts the output voltage V of the resistor R1 into a digital value and input it into an MPU 11. A key matrix 12 has a dimmer switch and plural channel switches. And, the MPU 11 has a function of presetting the output values of the A/D converter 20 under the indications of the dimmer switch and channel switches, and a function of reading out one of the preset plural digital values to carry out the control of the luminance of a display 13.
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