| abstract |
A method of detecting analog signal degradations in channel bank apparatus. The apparatus interconnects a digital PCM line with a plurality of analog trunks by means of multiplex circuitry and a plurality of channel units each comprising a PCM-to-analog signal receive path and an analog-to-PCM signal transmit path. A plurality of sequences of prescribed PCM test code words, wherein each sequence is amplitude plottable against time into a triangularized waveform cycle, are circulated via a loop-around path bridging the receive and transmit paths of a channel unit. A set of values, each corresponding to a type of analog signal degradation, is derived for each recovered word sequence, based on prescribed amplitude and slope characteristics of its waveform plot, and is averaged over the recovered sequences. If any average characteristic value is not within an expected tolerance of a corresponding prestored expected average value, a defective channel unit indication is displayed. |