Operating dial

An operating dial operated by rotation, comprising:

• a printed circuit board (10) having an electric circuit;
• a drive electrode (13) provided on said printed circuit board (10);
• a plurality of detecting electrodes (12) provided around said drive electrode (13) on said printed circuit board (10);
• ring electrodes (101, 101a) disposed in opposition to said drive electrode (13) across a gap, such that the ring electrodes (101, 101a) have at least one projection (102, 102a) projecting outward to oppose one of said plurality of detecting electrodes (12) across a gap;
• a dial made of an electrically insulating material, rotatable and integral with said ring electrodes (101, 101a);
• a drive circuit (200) for applying a high frequency signal to the driving electrode (13);
• a switching circuit (300) for sequentially connecting each of said plurality of detecting electrodes (12) and outputting signals from the connected detecting electrodes (12);
• and
• signal detection means (400) for processing output signals from said switching circuit (300) and detecting signals induced on the detecting electrodes (12) opposing the projections (102, 102a) on said ring electrodes (101, 101a) by using high frequency signals applied to said drive electrode (13), thereby outputting a detection signal corresponding to the dial operating position;
• wherein the drive circuit (200) includes:
• a square wave signal generating circuit;
• and
• an L-C resonance circuit for extracting the frequency component of high frequency signals applied to said drive electrode (13) from the square wave signal generated by said square wave signal generating circuit.