| 摘要 |
PURPOSE:To obtain a feeding circuit which can feed normal source voltage immediately when grounding is restored and whose protection network does not work in a momentary grounding state by providing a grounding detection means, the delay means of a grounding detection signal, feeding disconnection means and a protection means. CONSTITUTION:The feeding circuit consists of the grounding detection means 31 detecting that one of two telephone lines is in a grounding state, the delay means 32 delaying the grounding detection signal when the grounding is detected by the means 31 and the feeding disconnection means 33 disconnecting direct current feeding means 10 and 20 when the grounding detection signal turns on. Then the protection means 30 protecting the direct current feeding means 10 and 20 from excess current flowing at the time of grounding is provided. Therefore, when the grounding over the delay time of the delay circuit 32 occurs, the protecting operation is executed for the excess current flowing to the means 10 and 20 by making the means 10 and 20 into the disconnected state through the feeding disconnection means 33. Thus the feeding of the source voltage can be started immediately when the grounding state is restored and the protection means 30 does not work for the momentary grounding. |
