| 摘要 |
This unit is an automatic circuit switching device which performs synchronization of a regular circuit and a stand-by circuit to achieve switch back operation from the stand-by circuit to the regular circuits without any hit or short break of data transmission when the regular circuit is restored. Detectors 141, 142 output an instruction signal to establish a stand-by circuit when regular circuit 2 becomes disconnected and output an instruction signal to start comparison of synchronization when regular circuit 2 is restored from the disconnection, based on the results of monitoring of the signals. Terminal adapter circuits 151, 152 establish stand-by circuit 4 based on the instruction signal to establish the stand-by circuit and output switching instruction. Comparators 181, 182 control delay circuits 161, 162, 171, 172 based on the comparison start instruction and output switch back instruction when the above synchronization is achieved. Switching circuits 191, 192 transmit the output signals from delay circuits 171, 172 to the corresponding subscriber terminals based on the switching over instruction and transmit the output signals from delay circuits 161, 162 to the corresponding subscriber terminals based on the switch back instruction.
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