| 摘要 |
PURPOSE:To eliminate the necessity of a stationary monitoring station, by causing the data transmission station which is close to the point where a transmission fault occurs to send beacon data to other data transmission stations and performing restoring operations, such as loop switching, etc., of the system. CONSTITUTION:Usually, a token TK is held on a main transmission line A and the token circulates among the A-channel station of each of the 1st-5th stations. When a fault occurs between the 3rd and 4th stations of the main transmission line A, an A-channel token arrival monitoring timer TAT becomes a time-over state since the token TK does not arrive at the 4th station and the 4th station sends a beacon A-packet BAP. The BAP is successively transmitted to all stations from the 5th station on the downstream. Upon receiving the BAP, each station actuates an A/B-channel switching timer TC and after the time TC has passed, switching is made from the A-channel to the B-channel. The 1st station which is the then monitoring station actuates a token resending timer Ti simultaneously with the actuation of the timer TC and resends the token TK by using an auxiliary transmission line B after the Ti has passed.
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