| 摘要 |
A proximity switch e.g. for a domestic a.c. supply is connected in-line e.g. in the live line of the supply between live and switch live terminals. No direct connection is made to the neutral line. Switching is performed by a triac T which receives a gate input 17 from a control circuit K that includes a proximity switch (FIGS. 5, 6). The control circuit K has a power supply comprising a charge storage capacitor C1 that is charged from the live terminal through a first impedance (diodes D3, D4) and a unidirectional first path through diode D1 when the triac T is conductive. When the triac T is switched to a non-conductive state, the capacitor C1 is charged from the switch live terminal through a second unidirectional path including diode D1 and a second impedance R2.
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