| 摘要 |
PROBLEM TO BE SOLVED: To provide a no hit switching device with which switching at the time of erroneous multiframe synchronism detection can be prevented and the occurrence of hit on the downstream side can be prevented. SOLUTION: A multiframe synchronizing pattern inserting circuit 11 on a transmission side 1 inserts a multiframe synchronizing pattern to a main signal, and a multiframe synchronism monitoring pattern inserting circuit 12 inserts a multiframe number to the time slot of the main signal while counting it up. Multiframe synchronism verifying circuits 23 and 24 on a reception side 2 perform the count-up of the multiframe number based on write pulses from multiframe synchronizing detection circuits 21 and 22 and compare that count value with the multiframe number in the time slot of the main signal. When the compared result is erroneous, the multiframe synchronism verifying circuits 23 and 24 discriminate and report erroneous synchronism. When the erroneous synchronism is reported, a phase control/discrimination circuit 27 inhibits the switching operation of a selector 28. |
