METHOD OF CHANNEL DETERMINATION, METHOD OF CLOCK SELECTION, AND CHANNEL SWITCH DEVICE

摘要

A circuit switch device (22) includes a switch (60) for selecting the clock of an SDH transmission channel (32), the clock of a signal determined by a route switch (54), or the clock of an internal oscillator (62). The clock from the SDH transmission channel is selected when it is normal, whereas the clock of the internal oscillator is selected when the clock from the SDH transmission channel is abnormal. If the phase difference between the read and write of a buffer memory (58) exceeds a threshold thereafter, the switch selects the clock of the received signal determined by the route switch (54). The circuit switch devices at both ends of a transmission channel operate independently in such a manner, so that appropriate clock selection is achieved in switching channels.