| 摘要 |
PCT No. PCT/GB86/00562 Sec. 371 Date May 15, 1987 Sec. 102(e) Date May 15, 1987 PCT Filed Sep. 19, 1986 PCT Pub. No. WO87/01883 PCT Pub. Date Mar. 26, 1987.A proximity-switch circuit operates a main switch TH1 to pass an ac supply through an external load when a metallic object is near a coil L1 that is part of an oscillator circuit. The oscillator circuit is connected to a level detector circuit controlling the switch TH1. The circuit is powered by a power supply stage that includes a storage capacitor C7, for which the charging current is controlled by a transistor T10 and a MOSFET T11. Upon initial application of the ac supply, the level-detector circuit is overridden by a circuit that includes capacitor C3 and transistor T4 until a predetermined period of time has elapsed, so as to prevent the generation of erroneous "on" signals before the oscillator has stabilized.
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