| 摘要 |
PURPOSE:To prevent reduction in signal transmission ratio of a transformer coupling signal and to simplify the constitution of a connected interface by providing a transformer coupling interface and an interface without transformer coupling. CONSTITUTION:A line concentrator WC1 consists of a connector zMIC 21 connected to a transmission line 2 and ring branch lines 5, 6 a bypass circuit 2 by-passing the ring branch line, a by-pass control circuit 13 controlling the circuit 12, a transformer coupling interface connected to a ring branch line 5, a subline concentrator coupling interface section 11 and a transmission line control circuit 14. The subline concentrator PWC 4 consists of a connector 21 connected to the ring branch lines 5, 6 the transformer coupling interface section 10 connected to the ring branch line 5, and the interface section 15 connected to a host line concentrator or subordinate subline concentrator. The transformer coupling interface section 10 is provided with a transformer TRS, and a relay RY switching the transmission line to the branch line by the operating control section of the terminal device.
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