| 摘要 |
PURPOSE:To eliminate the need for a centralized control station and to structure a high-reliability network by detecting the 2nd upstream station by the 1st station on the basis of connection position information stored previously when a ring system network becomes abnormal and indicating the return of a signal to the 2nd station. CONSTITUTION:A station ST which detects abnormality on an in-use transmission line 2 starts a waiting timer for abnormality information frame reception, and when the timer TI enters a time-out state without receiving an abnormality information frame BCN1, it is judged that the ST is an ST adjoining to a faulty downstream station in a faulty state, the 1st returning operation is performed to generate a BCN2 containing information showing an ST at the downstream side of the ST is an ST which performs the 2nd returning operation, and a waiting monitor timer T2 for the reception of the BCN2 is started to send out the BCN2. When the BCN2 is received before the timer T2 enters a time-out state, the 2nd returning operation is carried out at the next upstream ST to form a closed ring.
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