Patent GB-683824-A (GB)
Title: Improvements in and relating to electric pulse code signalling systems
Inventor: LEVY MAURICE MOIESE
IPC: H04J3/00
Filed: 1950-03-07
Abstract: 683,824. Multiplex pulse code signalling. GENERAL ELECTRIC CO., Ltd. Feb. 21, 1951 [March 7, 1950], No. 5783/50. Class 40 (v). In a time division multichannel pulse code system the individual pulses of a code group for one channel are interlaced in time with those of another channel. In the embodiment described provision is made for seventy-two channels, the channel period being divided into twelve group intervals each of which accommodates six channel code groups with their individual pulses interlaced, and a sixunit binary on-off code is used. One group interval, e.g. GI1, Fig. 3, contains the pulses of three channels selected from the positive-going pulses of wave C and of three other channels selected from the pulses of wave D. The resulting code pulses are reduced to one-third of their original width by gating circuits supplied with pulses GP1, GP2, GP3 and GP4, GP5, GP6, respectively, so that the code pulses of the six channels interlace. At the transmitter, the distributer D1, Fig. 1, generates twelve interlaced pulse trains at channel recurrence frequency, the pulse duration being equal to that of one group interval GI1, GI2, &c. These pulse trains are fed to six twelve - channel amplitude - modulated pulse multiplexing circuits of which two, PMA and PMB, are shown, the twelve channel modulating signals being applied thereto over the conductors SA, SB, respectively. The channel pulses from PMA are sampled in gate circuit GA by pulses A, Fig. 3, from a generator PG1, the samples being coded in circuit CA by selection from pulses C, Fig. 3, also supplied by generator PG1. The resultant code pulses are narrowed in gate circuit G1, by pulses GP1, Fig. 3, derived from a further pulse generator PG2, and passed to the output mixer M for transmission. Pulses from all six multiplex circuits PMA, PMB, &c. are similarly coded and interlaced, three using sampling pulses A and coding pulses C and three sampling pulses B and coding pulses D from generator PG1, the final gating circuits G1, G4, &c. being fed with narrowing pulses GP1 ... GP6, respectively, from generator PG2. A synchronizing signal is transmitted which may consist of a characteristic modulation, such as a pulse and no pulse occurring alternately in code pulse intervals recurring at channel recurrence frequency. At the receiver, Fig. 2, the incoming pulse train at terminal T is fed to the six gating circuits GR1 ... GR6, to which are applied, respectively, the pulses GP1 ... GP6, Fig. 3. These are derived in generator PG3 from the synchronizing signal selected in circuit SL also fed with the incoming pulse train. In order that identical decoding pulses may be supplied to decoders DC1, DC2, DC6 and to decoders DC3, DC4, DC5, delay circuits DL1, DL3, DL4, DL6, are provided between the gate circuits GR ... GR6 and further gate circuits GS1 ... GS6 preceding the decoders and grouped similarly, the groups being provided with gate pulses GP2 and GP5, respectively. Each decoder provides amplitude-modulated pulses corresponding to twelve interlaced channel pulse trains, the channels being separated in distributers DR1 ... DR6, respectively. Specification 683,820 is referred to.