GB1494894A - Transmitters for conductor identification in multiconductor electric cables and systems and methods employing same - Google Patents

Abstract

1494894 Selective signalling POST OFFICE 20 Feb 1975 [28 Nov 1973] 55203/73 Heading G4H A shift register enables a plurality of gating circuits to pass oscillator bursts of different durations respective to the gating circuits. One of a plurality of conductors (or pairs of conductors) is identified by applying to each conductor a burst signal of duration unique to that conductor and at a receiver identifying a conductor in response to the duration of the signal on it. An oscillator (of higher than specch frequency) drives a shift register via a divideby-16 circuit to enable progressively more of 20 gates (i.e. the first, then the first and second, then the first, second and third, and so on) to pass the oscillator output rounded to a sinusoid to 20 conductors respectively (e.g. conductors in a telephone cable), the sequence being repeated after a delay. A remote receiver is connected to one of the conductors to be identified, the signal being filtered, squared then sent in parallel to a noise discriminator and counter means. The counter means consists of a divide-by-16 counter (which initially divides by 12 instead in view of possible loss of signal due to momentary line breaks) feeding a BCD counter. The noise discriminator starts with a retriggerable monostable with a period just longer than two cycles of the oscillator to detect the signal and ignore noise spikes. At the end of the signal it enters the count in the BCD counter into latches then resets both counters. The latch contents are decoded to drive a gallium arsenide 7-segment display, the decoder being disabled when no repetitive signal is being received.