| 摘要 |
PURPOSE:To omit a latch circuit and to simplify the overall constitution of a device by using a discriminator which secures a detecting/holding function for full waveheight in an amplifier and discriminates the output with the prescribed reference voltage. CONSTITUTION:An electrostatic capacity type keyboard consists of a control means 20, a drive circuit 22, a variable capacity switch matrix 24, a selector 26, etc., and recognizes the operating state of the switch selected by the means 20. Here an amplifier 36 having a full waveheight value detecting/holding function is provided together with a discriminator 38 which discriminates the output 37 of the amplifier 36. The amplifier 36 holds the peak value through an integration circuit consisting of a resistance 43 and a capacitor 44 and supplies the output 37 to the discriminator 38. Thus only the signals having levels higher than the prescribed reference voltage are discriminated. This improves the noise resistance and simplifies a control signal system.
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