GB1485877A - Transmission systems - Google Patents

Abstract

1485877 Testing pulse regenerators SIEMENS AG 18 Dec 1974 [31 Jan 1974] 54804/74 Heading H4L The invention relates to an arrangement for locating faulty pulse regenerators in a P.C.M. transmission system of the type disclosed in Specification 1,212,908. In that Specification the fault detecting arrangements incorporate demodulators and associated band pass filters of different pass frequencies at respective intermediate stations of the system, together with arrangements for transmitting from an end exchange a pulse train consisting of code elements modulated such that the frequency of the envelope curve corresponds to the pass frequency of the band pass filter at a particular station to be tested. The present invention is concerned with the means for producing the test pulse pattern. The test pulse pattern generator comprises a fundamental pulse pattern generator 22 whose pattern bit rate corresponds to the normal data flow and contains a sync. signal consisting of pairs of code elements 11 and 00 arranged in alternating sequence and spaced by other code elements. The generator also comprises a binary counter 21 and switches 19 for setting the counter to a selected numerical value (corresponding to the regenerator to be tested). In operation the counter counts from the set value to a final value. A low frequency rectangular waveform generator 24 is responsive to the counter reaching the final value and produces a frequency (corresponding to the pass frequency of the filter in the selected regenerator) which modulates the fundamental pulse pattern. A pulse generator 23 supplies control pulses to the fundamental pulse pattern generator, the counter and the rectangular waveform generator. The rectangular waveform is arranged by switching to have either a mark/space ratio of 1 : 1 or other than 1 : 1. A switch 27 and gate 25 are provided for gating "fault" pulses into the pulse pattern.