| 摘要 |
PURPOSE:To quicken the processing at a fault by holding a clock for a prescribed time after the clock interruption is detected when the clock given from plural stations connected as a ring is turned off and applying the fault processing during the holding. CONSTITUTION:A signal from an upperstream station ST4 is received (5) in a station ST1 in ring form connection, the signal is detected (6) to extract (7) the clock. The signal level and the clock level are compared (9, 10) with reference voltages 11, 12 a gate 13 applies logic to decide the period of fault detection and synchronization holding. The state is inputted to a control circuit 17 to select the reception clock stored in a selector 15, a selector 18 selects the output of a pattern generator 16, the result is modulated (16) and sent (20). When out of synchronism is detected (10), a control circuit 17 stops the signal transmission toward the down-stream. Thus, the control at fault is quickened and the effect onto the entire system is decreased.
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