| 摘要 |
An analog keyboard for a video display appliance which serves to minimize the number of control switches has one or more sections 100 (only one shown) connected in parallel to an A/D converter 1. In each section 100, rotation of a control switch 2 clockwise or anticlockwise produces two pulses P1,P2, which occurs first depending on the rotation direction. After noise elimination at 3a,3b, one of two multivibrators 4a,4b is triggered to disable the other and enable one of two circuits 5a,5b to provide a respective voltage to the A/D converter 1.
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