| 摘要 |
PURPOSE:To speed up the switching of loop at failure, by taking a state of loop back mode at an upper side from a failed point and taking a state of return mode from the lower side. CONSTITUTION:The frame information is circulated via a loop transmission path 3-0. Further, the clock detection circuits 16-0-16-3 for loop transmission units 2-0- 2-3 monitor the circulation of the frame information. Further, when a disconnection is caused, the circuits 16-3 and 16-0 switch the return switching section S1. Next, the maintenance control adaptor 4 of the unit 2-0 designates the unit 2-2 to output the loop back control instruction and switches the loop back switching section S2. Thus, the disconnected position is automatically avoided to form the loop using transmission lines 3-0 and 3-1. |
