Societe Anonyme De Telecommunications

Guy A De Passoz

Xavier N Barbier

Andre A Aveneau

The present invention relates to the D.C. supply for a subscriber control system, and consists essentially in supplying the control system from the exchange solely in response to a request, such request being emitted either by the exchange or by the control system, a preamble message being emitted in-line by the control system in order to initialize a communication in the latter case. The invention is applicable to the digitalization of the subscriber's telephone.

Supply for a subscriber control system

A process for the compression of signalling data or the like transmitted in a stream of digital PCM information organized in multiplexing frames, the signalling data being inserted in a specific time slot of the PCM frames, the signalling binary digits transmitted in the same PCM frame belonging to independent signalling channels a, b, . . . of rate H.sub.1, comprising the steps of extracting the signalling data from the digital stream and effecting in parallel, for each signalling channel, a processing comprising the steps of coding the transitions by a group of binary digits of which the first indicates the polarity of the transition and the following indicates or indicate in which nth fraction of a clock period corresponding to a rate H.sub.1 /n the transition is located, and transmitting unchanged at least one of the bits which follow the transition, the signals L.sub.a, L.sub.b . . . thus obtained containing the same quantity of information as the signalling channels, but having a rate divided by n.

Process for the compression of signalling data or the like transmitted

The common return path of a circuit for applying pulses in alternating polarity to the balanced input transformer of a bipolar code signalling circuit is switched to block the first half and pass the last half of each pulse with a timing independent of polarity. The pulses supplied to the switched pulse-applying circuit have the same duration as the binary signal pulses from which they are derived, but these binary signal pulses are alternately supplied to the two sides of the pulse applying circuit by means of an AND-gate and a multivibrator. The same clock pulse generator times the multivibrator and the common path switching of the pulse-applying circuit. The circuit converts binary to bipolar signals free of asymmetric timing errors.

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Lesigny, France

Guy A De Passoz