JPS5721148A - Monitor system for pcm relay transmission line - Google Patents

Abstract

PURPOSE:To monitor misconnection at the connection point between a balanced pair cable on a transmission line and a relay device, by adding a polarity detecting circuit of PCM code to each relay device. CONSTITUTION:When a low frequency alternating pulse train (a) is applied to a transformer 30, the part of positive polarity is reproduced as (b) with a polarity pulse identifying reproduction circuit 36 and the part of negative polarity is reproduced as (c) with a negative polarity identifying reproduction circuit 38. The output of the reproduction circuits 36, 38 is rectified as (d), (e) with rectifying circuits 46, 48 and compared at a comparator 50. In this case, when no misconnection is present, the (e) is almost constant and the waveform of (f) almost the same as the (d) is obtained at the secondary output of a transformer 52, but if there is misconnection on the way of transmission line, since the pulse train inverting the signal (a) is inputted, the (d) is almost constant this time, resulting that the secondary output (f) of the transformer 52 is almost constant. Thus, no low frequency of (f) is detected, then it is known that misconnection or any failure is present.