| 摘要 |
PURPOSE:To secure many channels that allow speech between subscribers of a line concentrator even at the time of trouble by preparing a turn back highway that is locked in phase with a down line concentration highway in the output side of an up line concentration switch, and connecting a highway selectively. CONSTITUTION:In case where all line concentration highways are normal, the number of channels that allows speech between subscribers included in the line concentration switch is the sum of number of channels of turn back highway tbc and down line concentration highways tba, tbb. In case where the line concentration highway goes wrong and speech through a distributing step is made impossible, the number of usable channels becomes the sum of turn back highways tbc and tbi by controlling a selector circuit S and selectively outputting the turn back highway tbi. |
