| 摘要 |
PCT No. PCT/GB93/01717 Sec. 371 Date Feb. 24, 1995 Sec. 102(e) Date Feb. 24, 1995 PCT Filed Aug. 13, 1993 PCT Pub. No. WO94/05108 PCT Pub. Date Mar. 3, 1994A maintenance termination unit (MTU) for use in telephone circuits. The MTU comprises a switching arrangement which can be connected in a communications channel, the communications channel comprising a pair of lines. The switching arrangement is connected between a set of exchange-side terminal equipment and a set of subscriber-side terminal equipment. The arrangement comprises first and second line switches, each of which is series connected in one of the lines. Each line switch comprises a control terminal, and has a closed state in which it will pass normal line current, and an open state in which it will pass at most a reduced line current. The arrangement also comprises a control circuit which is connected to the channel between the line switches and the subscriber-side terminal equipment. The control circuit comprises: a charge reservoir which is connected between the lines; a reservoir charging switch which is connected in series with the charge reservoir and controls the charging of the reservoir in response to a signal on the lines; and a reservoir discharging switch which is controlled by a signal on the lines and will allow the reservoir, when charged, to energize the control terminals of the line switches so that, when the line switches are opened by the control circuit, the line switches can be maintained in an open state for a period of time by discharging the reservoir.
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