| 摘要 |
PURPOSE:To constitute a loopback path if a fault takes place by providing a switching switching an input from a left system loop transmission line and an input from a right system and providing a specific control means. CONSTITUTION:Switches 60-67 switching the input from left system loop transmission lines 100-102 and an input from right system loop transmission lines 200-202 are provided in nodes 10, 11. Moreover, control means 40, 41 are provided and if any of left or right system transmission/reception processing sections 20, 21, 30, 31 is faulty or any of them is not provided, the switches 60-67 are controlled to input the input from the loop transmission line to the normal transmission/reception processing sections 20, 21, 30, 31 if the loop line 400, 401 is faulty. Thus, the constitution of the loopback path is attained.
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