| 摘要 |
PROBLEM TO BE SOLVED: To perform switching from the current transmission line to a spare one to prevent cell duplication and to construct a device in a small scale. SOLUTION: The current and spare cell processing means 102 and 104 recognize timing at which cells are received on a fixed transmission cycle from the current and spare cell transmission lines 101 and 103 by detecting an area where cells in what divides the inter-change point of a transmission period into plural areas are received, and output these cell receiving timing information to a controlling means 106 through a control bus 105, and when the means 106 compares both cell receiving timing information to recognize that the respective means 102 and 104 receive the same cell in different sections, the means 106 notifies the means 102 of an instruction that cells are transmitted to the line 101 up to the change point to be a switching point and that cells are discarded afterward and notifies the means 103 of an instruction that cells are discarded up to the next change point of the switching point and that cells are transmitted to the line 103 after the change point.
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