| 摘要 |
PURPOSE:To attain diagnosis at the time of operation without disturbing a call of a subscriber by intermitting the diagnosis when a call during the diagnosis is detected to restore the subscriber line to the state before the start of diagnosis. CONSTITUTION:A diagnostic device 11 is provided with a test use termination circuit terminating the subscriber line being led in, a test signal generating circuit and a scanning signal read circuit or the like so as to apply a channel test or the like by means of the loopback of the test signal and a scanning test. When a subscriber telephone set makes a call during the diagnosis, a call supervisory device 12 detects the call and informs it to a control device 13. When the device 13 receives the notice, the device 13 makes the device 11 intermit the diagnosis and throw changeover contacts 21a, 22a of a subscriber circuit 2a into the state before the start of diagnosis. A BORSCHT section 5a in the circuit 2a detects the call, it is informed to a common controller to start a conventional call processing. After the talking is finished and the absence of talking is confirmed again, the diagnosis by the device 11 is restarted.
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