Pseudo-random multiplex synchronizer

Claim 1

A time division multiplex signal transmission system using pulse code modulation, in which the transmitter comprises a plurality of channels for the information signals and at least one synchronizing channel to which a pseudo-random signal generator applies the multiplex synchronizing Code pulses, the information signal pulses and the synchronizing code signals being cyclically distributed in time within the frame period by means of a channel distributor operating at clock-pulse frequency, while the receiver comprises an extractor for recovering the clock frequency from the received multiplex signals and further, like the transmitter, a plurality of channels for the information signals and at least one synchronizing channel, the received multiplex signals being cyclically distributed in time by means of a channel distributor under the control of the recovered clock pulses, the receiver finally comprising an arrangement for synchronizing the channel distributor of the receiver with the channel distributor of the transmitter, characterized in that the receiver synchronizing arrangement comprises a local code generator which supplies at m outputs m mutually shifted copies of the synchronizing code, the shifts being equal to a given number of bits of this code, each of these m outputs is connected to one input of one of m modulotwo adders the other input of which is connected to the combined outputs of the channel commutation switch, the outputs of m adders being each connected to the input of one of m groups which each comprise n counters, which counters are all reset to zero at the beginning of a copy produced at a reference output of the local code generator, and each are provided with an output for a predetermined counting threshold, the outputs of the adders are connected to the inputs of the counters by means of a logical arrangement which is controlled by the output signals of the channel distributor circuit in a manner such that in order to compare m given copies with the signals of all the N channels of the multiplex the n counters of each group of counters are connected to the associated adders, first in the time intervals of the n channels of each group of n channels during a synchronizing code which appears at the said reference output, then in the time intervals of the n channels of the given number of other groups of n channels during a given number of consecutive synchronizing codes which appear at the said reference output, the number of synchronizing codes and the number of groups of n channels being so chosen that the time intervals of all the channels are utilized, the synchronizing device of the receiver further comprises a circuit for controlling the shifting of the local code generator and a circuit for controlling the shifting of the channel distributor, which circuits are connected to the outputs of the counters and are arranged so that when at the end of a cycle of comparison of m given copies with the signals of the n channels of the multiplex the thresholds of all the counters are reached, the local code generator is shifted so as to provide m further copies, and that, when at the end of a synchronizing code produced at the said reference output the counting threshold is not reached in a counter which corresponds to a given channel and to a given copy, the local code generator and the channel distributor are shifted so that the said channel is made to coincide with the synchronizing channel and the said copy is produced at the said reference output of the local code generator.

Claim 6

A system As claimed inin which one of the frame channels is a sub-multiplexedchannel in one part of which is applied, at the transmitterend, a synchronizing code for the sub-frame definedby the channel, characterized in that the receivercomprises a sub-frame synchronizing device having thesame structure as the frame synchronizing device.