Plessey Handel Und Investments A.g.

Velauthar Kopalapillai Thillainayagam

Douglas Stanley Larner

Ronald William Blackmore

Barry Michael Hill

A repeater for a digital data-transmission system using a disparity-displaying digital code comprises a digital regenerator and error-detecting means therefor and in which supervisory control means incorporated in the repeater is operative upon reception of an interrogate pulse signal over one access path also used as a digital-data path, to cause a response signal to be returned over the access path according to the prevailing state of the error detecting means. The response signal comprises a different number of pulses for each of the two possible output states of the error detecting means. The repeater may be the first of a pair of repeaters of a particular repeater station, both repeaters including at least substantially identical digital regenerators and error-detecting means. The repeaters are incorporated in different digital data-transmission paths and are so interconnected that the reception of an interrogate pulse signal by the first repeater is effective in that the aforesaid response signal takes into account th prevailing state of the error-detecting means serving the digital regenerator of the second repeater.

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Maidenhead, United Kingdom

Velauthar Kopalapillai Thillainayagam