| 摘要 |
PURPOSE:To supply power to a network terminating section and a terminal section only when communication is conducted by providing a polarity coincidence circuit to a network termination section and controlling the start of the polarity coincidence circuit based on the closing of a start switch of the terminal section and an incoming signal from an exchange. CONSTITUTION:When the start switch 12 of the terminal section 8 is turned on at calling, since points (a) and (b) of the polarity coincidence circuit 13 of the network terminating section 1 are short-circuited via a line 6, power is applied to a power supply circuit 3 from the exchange to a power supply circuit 3 of the network terminating section 1. Further, the power from the exchange is applied simultaneously to a power supply circuit 10 of the terminal section 8 via a path of 1st AC/DC separating circuit 2 of network terminating section 1 - polarity coincidence circuit 13a - line 6 - start switch 12 of terminating section 8 - AC/DC separating circuit 9 - line 6 - 2nd AC/DC separating circuit 5 of network terminating section 1 - polarity coincidence circuit 13b - 2nd AC/DC separating circuit 5 - line 7 - AC/DC separating circuit 9 of terminal section 8 - power supply circuit 10. When the terminal section 8 receives an incoming, the power is fed similarly to the network terminating section 1 an the terminal section 8.
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