| 摘要 |
A bidirectional line switched ring network having a path alarm indication signal (AIS) generation function, which is provided with ID writing means for writing, in the path overhead bytes of frames, IDs preassigned to add side nodes, tables for holding the correspondence between the IDs of add side nodes for sending frames to be dropped at drop side nodes and the number of the time slots to be used for the transmission of the frames, comparing means for comparing the IDs of the add side nodes read from the received path overhead bytes and the IDs in the tables corresponding to the number of the time slots used by the received frames, and path alarm indication signal generation means for generating and sending a path alarm indication signal (AIS) when the result of the comparison is that the two IDs do not match. By this, a path alarm indication signal can be generated at a high speed at the time of erroneous channel connection by simple hardware and a simple procedure.
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