| 摘要 |
<p>A residual current operated device includes a d.c. power supply (36, 38, 40) and means (82) for inhibiting the supply of d.c. power to the operational part of the device until the magnitude of the d.c. voltage is equal to or greater than a predetermined value. The inhibiting means comprises a serial electronic switch (84) coupled between the d.c. source and the device, the switch being arranged to close when the d.c. voltage applied to it is equal to or exceeds said predetermined value.</p> |
