Improvements in or relating to communication channels conveying information in the form of a code

771,302. Code telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Dec. 10, 1953, No. 34416/53. Addition to 721,838. Class 40 (3). A telegraph receiver for equal length combinations of elements of two signalling conditions having a time scale circuit driven by regularly repeated pulses and providing pulses for examining the condition of the incoming signals at predetermined instants and effecting their regeneration comprises means for recording whether transitions from one signalling condition to another occur early or late in respect of their nominal positions in the time scale and means for momentarily stopping and restarting the time scale circuit independently of the transmitter and of the received signals and means for adjusting the position in the time scale at which the time scale circuit is restarted under control of said recording means. The arrangement is described in connection with the telegraph system of Specification 771,301 in which two check pulses are added to the normal five-unit code and in which the idle condition is represented by a continuous marking condition, whilst the seven-unit combination MMMMMSS is transmitted preparatory to the transmission of information. The transition from mark to space will therefore occur at 100 ms. from the commencement of the normal time scale in a cycle of 145 ms, if the seventh element is assumed to have a duration of 25 ms. In the rest condition, switch 12F has element 1 conducting and when the line changes to space, gate 101G passes a pulse to gate 105G which also receives a pulse 11fsp switch 11F which normally has its element SP conducting. Element ST of switch 11F is made conducting and produces a pulse 11ft which opens gate 102G since switch 23F is assumed to be in its position 23F4. The counter 11C which receives pulses at a frequency of 5Kc is started at position 102 ms. from zero. To guard against a false start occasioned by a space occurring in the normal idle signal the incoming signal is tested at 105 ms. and at intervals of 5 ms. up to 140 ms. by a gate 104G, and if a mark is present at two of these instants, a counter 12C is stepped to position 2 and via gates 108G, 107G operates switch 11F to make element SP conducting and close gate 103G to the stepping pulses - P. A pulse 11ft produced by the change-over of 11F resets the counting circuit 11C to position 102 and the counter 12C to the position 0. The received elements are applied to a switch 21F which produces an output at 21ft at each chan