| 摘要 |
PURPOSE:To miniaturize a subscriber circuit by providing one set of a ring trip circuit in common to plural subscriber circuits to eliminate the need of an exclusive ring trip circuit at each subscriber circuit. CONSTITUTION:The ring trip circuit 1 is provided in common to n-set of subscriber circuits 11. When a transmission control signal SD is intermitted in a subscriber circuit 11i calling an allocated subscriber 2, an RG relay 7i is intermitted by a ring trip control circuit 12i and a call signal fed from a call signal source 8 to the allocated subscriber 2i via the ring trip circuit 1. When the subscriber 2i responds to the call, the ring trip circuit 1 detects the off-hook state and a trip signal TRP is sent to a ring trip control circuit 12 of each subscriber circuit 11. Then the RG relay 7i is restored, the transmission of the call signal is stopped to connect the subscriber 2i to a feeding supervisory circuit 9i to supervise the off-hook state of the subscriber 2i. When the circuit 9i detects the off-hook of the subscriber 2i, the ring trip control circuit 12i stops the call signal transmission control to the subscriber 2i further.
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