| 摘要 |
After marker functions have been performed to set up a network path during normal call processing, a continuity word is inserted into the path. The output of the path is coupled back to the input via a test multiplexer at the input to circulate the continuity word. A word is taken from the path being tested after circulation and is compared to the original continuity word, with identity of comparison being verification of continuity. Continuity test apparatus includes a continuity word register and a comparator. The comparator has inputs from the continuity word register and from the network output for the path being tested. The continuity word may be inserted in the path from an output access memory for maintenance and test words, having its output to the same multiplex lead as the output buffer memory. The continuity word may also be taken from the continuity word register, and from there supplied to a third input of the test multiplexer, and this input is enabled during the time slot of one frame to insert the continuity word. If the network includes access from a controller to input and output buffer memories, the continuity test apparatus may be omitted, and direct reading and writing of the buffer memories used to insert and extract the continuity word from the path being tested, and the comparison is then done in the controller. The test path may also be extended via TDM digital lines to a remote line switch, where the outgoing channel is coupled back to the incoming channel in response to continuity test commands.
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