Patent GB-803804-A (GB)
Title: Improvements in or relating to electric multichannel pulse communication systems
IPC: H04J3/10
Filed: 1956-06-18
Abstract: 803,804. Multiplex pulse signalling. COMPANHIA PORTUGUESA RADIO MARCONI. June 18, 1956 [June 20, 1955], No. 18763/56. Class 40 (5). Relates to multi-channel timedivision pulse communication systems with redundancy-reducing arrangements, in which quantized signal-amplitude samples for n channels are transmitted between each pair of marker signals, Fig. 1, in some cases by pulse interval modulation and in others by pulse code modulation depending upon the probability of the sample amplitude to be transmitted. For example, in the complete pulse train cycle shown, provision is made for a maximum of eight time quantum intervals between a pulse of one channel and the preceding pulse for the first n pulses in the cylce corresponding to the n channels. The information concerning the channel samples thus transmitted is in the form of a code in which an interval of one time quantum represents the highest probability, namely zero amplitude, and an interval of two time quanta indicates the second highest probability, namely that the sample value is greater than that represented by seven quantum steps and will be transmitted after the first n pulses as a binary code (PCM) group of pulses. An interval of three time quanta indicates the third highest probability which may, for example, be the amplitude level one or a predetermined medium amplitude level and so on up to the eighth highest probability corresponding to an interval of eight time quanta. The second case is represented by the pulses in channels 3 and 7 which follow at intervals of two time quanta after the respective preceding channel pulses. The PCM groups 12, 13 belong, therefore, to channels 3 and 7, respectively, and are transmitted, together with channel identifying signals, as described in Specification 694,951. The system may be arranged to transmit changes only in the values of the channel signal samples and the provision of service signals to indicate the sense of the change is discussed. One channel circuit is shown in Fig. 3, in which the modulating signal is applied at 14 to two sampler valves 29, 38 gated open at appropriate instants at their suppressor grids. A gating pulse is applied to sampler valve 29 through transformer 31 upon the simultaneous receipt by valve 27 of the output pulse from the preceding channel at input terminal 28 and a clock pulse at 25 from a central timer. If the sample pulse amplitude is zero the multivibrator 36 is not disabled and the gate pulse from secondary 37 of transformer, 31 triggers it to produce a pulse at output terminal 28 one time quantum after the pulse arriving at input terminal 28. At a sample level corresponding to nine time quanta or more the multivibrator 35 is triggered to produce a pulse at output terminal 28 occurring two time quanta after the initiating pulse and applied also to terminal a of an electronic distributer to reserve a transmission interval for PCM group after the nth channel pulse has been transmitted. For intermediate sample amplitudes the amplitude quantizer 37 fed with clock pulses from terminal 25 feeds to the output terminal 28 a channel pulse exactly three, four ... eight time quanta, according to the sample input, after the previous channel pulse. The sampler valve 38 sends a signal sample for the PCM coding over the distributer terminal c when gated open by a pulse from the distributer terminal b. The distributer may be as described in Specification 694,951. Schematic layouts of the complete transmitting and receiving equipment are described, Figs. 2, 4 (not shown).