| 摘要 |
PURPOSE:To attain sure switching without stopping a transmission signal at the time of fault by providing a fault generation detecting circuit separately to a line of an active system and a stand-by system and switching the detected output from the active system to the stand-by system when the output is counted twice or over. CONSTITUTION:Fault generating detection circuits 25a, 25b are provided respectively to transmitters 22a, 22b of the active system and the stand-by system. When the circuit 25a detects generation of faults of a transmission line, the detection signal is fed to a count discrimination circuit 26a, where it is counted. When the count value reaches twice or over, the circuit 26a drives a relay 27, the contact 27a is closed and a contact 27b is opened. Thus, a relay 32 is energized, a switch contact 35 is changed over and the transmission line is switched from the active system to the stand-by system. In increasing the sum between the fault detecting time and the switching time more than the transmission time difference between the active system and the stand-by system, the transmission fault is not generated for the automatic switching of the transmission line at generation of fault. |
