GB689380A - Method of modulation and demodulation for pulse-type telecommunication system - Google Patents

Abstract

689,380. Multiplex pulse signalling. COMPAGNIE INDUSTRIELLE DES TELEPHONES. Jan. 11, 1952 [March 10, 1951], No. 927/52. Class 40 (v). Position - modulated pulses are produced by adding to an unmodulated pulse train, pulses derived by differentiating amplitude modulated pulses of the same phase and recurrence frequency. Demodulation is effected by integrating the sum of the modulated pulse train and an unmodulated pulse train of opposite polarity and the same recurrence frequency and mean phase. In the embodiment described one go and return terminal channel circuit of a multiplex communication system is shown inside the frame of dotted lines, the remainder of the circuit being common to all the channels at the terminal. The master oscillator 1 controls a pulse generator 2 which energizes the synchronizing pulse generator 3 connected to the outgoing line. Generator 2 also feeds the delay line distributer 4, from a tapping on which a pulse train is fed to the amplitude modulator 8 supplied with voice current from the hybrid transformer 9. The amplitude modulated pulses together with those from the other channel circuits are fed through valve 11 to the short-circuited line differentiator 12. The resulting pulse train is added to an unmodulated train derived from all the tappings on the distributer 4 through resistances 14, and fed to the limiter valve 15 and thence to line. Modulated pulses from the incoming line are applied to the synchronizing pulse separator 18, the output pulses of which are fed to the delay line distributer 19. The unmodulated pulse train derived through resistances 20 from all the delay line tappings is applied through limiter 21 to the grid of valve 17, together with the opposite polarity modulated pulses from transformer 16. The combined pulses are integrated by the open line 22 to produce amplitude modulated pulses which are fed to all the channel gating circuits. In the channel circuit shown the gating takes place in circuit 25 which receives gating pulses from one of the tappings on line 19. The output pulses are fed to a low-pass filter 28 and the recovered voice signal is passed to the hybrid transformer 9.