| 摘要 |
PURPOSE:To prevent a signal of prescribed frame constitution from being missing even when a signal series is subject to switching by selecting and sending a signal from a main transmission line stored in a frame buffer over one frame if a lobe is faulty. CONSTITUTION:A signal from a sub loop received normally by the 2nd signal system 12 and stored in the 2nd frame buffer 38 one by one frame each is selected by a selector 44 in a sub loop branch station and the result is sent to be station of the next stage. If a faulty sub loop is detected, a signal received by the 1st signal 11, stored in the 1st frame buffer 28 over one frame and read out to a parallel/serial conversion circuit 42 is selected by the selector 44 as the result. Thus, the signal is sent to the main transmission line without causing any missing in the signal by one frame in the timing synchronously with the signal transmission so far.
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