Adjacent switch

Abstract

PURPOSE: To prevent the mutual interference of an adjacent switch with simple circuit configuration by fluctuating the oscillation frequency of the adjacent switch with the lapse of time. CONSTITUTION: When a power source is turned on, the oscillation circuit 3 of a detection part 2 starts oscillation at a first frequency, the lamp waveform oscillation circuit 11 of a direct frequency modulation part 10 is simultaneously activated, the amplitude is changed with the lapse of time, and a second high-frequency signal lower than the first frequency is outputted to a vari-cap diode D. Based on the change of the signal, the vari-cap diode D modulates the first frequency of the detection aprt 2 to a direct frequency as the oscillation frequency to be fluctuated within a prescribed range. Then, a detection/integration circuit 4 detects the amplitude of the oscillation frequency modulated to the direct frequency, outputs a DC voltage integrated while responding to a frequency lower than the second frequency to a comparator circuit 5, compares the voltage with a reference level and detects the approach of a reagent. Namely, the oscillation frequency of the adjacent switch is fluctuated with the lapse of time, time for making adjacent the oscillation frequencies each other is shortened, and the mutual interference can be prevented. COPYRIGHT: (C)1992,JPO&Japio

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