| 摘要 |
The circuit is for transmitting the voice signal and signalling through the different typed lines; the trunk and the tie line trunk. The switches of the interfacing circuit are operated to adapt to the transmission line type. The circuit interfaces a station using the positive power as B/W loop power and a station using the negative power. The circuit includes a first switch which common terminal, a first and a second terminal are connected to a first relay, a transformer, and M line respectively to switching the common terminal input, a second switch which first terminal and second terminal are connected to the transformer (T1) and the earth line respectively, a ring signal attenuator (50) for limiting the level of pulse input through the second terminal of the first switch and a third switch which common terminal is connected to the transformer (T1).
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