Methods and apparatus for detecting and locating cable failure in communication systems

In a switching center, a test circuit including a signal detector and a signal generator and monitor connected through a switching device to cables interconnecting the switching center and remote terminals, a method for detecting which cable end has failed and a local access provider operating the failed cable, comprising the steps of:

• a) transmitting a data signal Ds at a desired signal level on the cables;
• b) recognizing a loss of the desired signal level on the cables exceeding a threshold as indicative of a failed cable;
• c) operating the switching device to connect the signal generator and monitor to the failed cable when the threshold is exceeded;
• d) generating and transmitting a reference signal Rs to the failed cable:
• and
• e) comparing in amplitude and phase the Ds and Rs signals on the failed cable to determine (i) if the cable failure occurred at the remote terminal or far end, or (ii) the switching center or near end of the failed cable, and (iii) the local access provider operating the failed cable.

Apparatus for detecting and identifying a cable end and local access provider of a failed connection between a switching center and a remote terminal comprising:

• a.) means for operating a cable between the switching center and a remote terminal at a desired signal level for a data signal Ds having amplitude and phase;
• b.) a signal detector and a signal generator and monitor connected to one end of the cable through a switching device;
• c) means included in the signal detector for recognizing the loss of signal level exceeding the threshold indicative of a cable failure;
• d) logic means connected to the signal detector for activating the switching device when a signal loss indicative of a failure has occurred on the cable;
• the switching device normally connecting the cable to the signal detector until activated by the logic means whereupon the switching device connects the signal generator and monitor to the failed cable;
• e) means, in the signal generator for generating or transmitting a test signal as a reference signal Rs and having amplitude in phase to the failed cable;
• and
• f) means, in the monitor, for comparing amplitudes and phase of the Ds and Rs to determine (i) if the cable failure occurred in the remote terminal or far end, or (ii) the switching center or a near end of the cable, and (iii) the local access provider operating the failed cable.

In a switching center, a test circuit including a signal detector and a signal generator and monitor connected through a switching device to cables interconnecting the switching center and remote terminals, a method for detecting which cable end has failed and a local access provider operating the failed cable, comprising the steps of:

• a) activating the test circuit to determine whether an interconnecting cable has failed;
• b) recognizing a signal loss in a data signal Ds having amplitude and phase in an interconnecting cable as indicative of a failed cable at one of the cable for test purposes;
• c) activating the switching device to connect the failed cable to the signal generator and monitor;
• d) transmitting a reference signal Rs having amplitude and phase to the monitor from the signal generator;
• and
• e) comparing the amplitudes and phases of the Ds and Rs signals at the monitor to determine whether the failed d cable has occurred at the switching center or at the remote terminal and the local access provider of the failed cable.