Patent GB-635488-A (GB)
Title: Multichannel electric pulse communication systems
IPC: H01J31/04
Filed: 1946-11-18
Abstract: 635,488. Multiplex pulse signalling. STANDARD TELEPHONES & CABLES, Ltd. Nov. 18, 1946, No. 34087. Convention date, Dec. 4, 1945. [Class 40 (v)] A multi-channel electric pulse communication system comprises means for producing a group of interleaved trains of signal-modulated pulses all having the same given repetition frequency, one or more of the trains comprising a sub-group of interleaved trains of signalmodulated pulses all having a repetition equal to a submultiple of the given repetition frequency. Fig. 1 shows a system for producing a multi-channel pulse time modulated wave containing two groups of signal channels, one group having a wide frequency band and a synchronizing channel, and a second group having a narrow frequency band, e.g. telegraph signals, which replaces one of the channels of the first group. A base wave source 2 is used to provide two sine waves with a phase difference of 90 degrees to the deflecting plates of electron tube 1, so that the beam rotates over the apertures in plate 10. Each separate beam impulse is deflected by the appropriate electrode on deflector plate 11 according to the signal energy from each channel. The beam is then applied to plate 12, which has a slanting, S- shaped narrow slot appropriate to each channel, so that time-modulated pulses may be taken from the secondary emission plate 19 for application to cathode follower 30. The final output is taken from lead 31 for transmission after treatment by a frequency modulator (not shown). The synchronizing pulses are produced by a pair of closely-spaced parallel slots 21 in plate 12. Specifications 603,188 and 635,482 are referred to. A similar system involving tube 32 is used to provide a further multi-channel train of pulses, but by means of frequency-divider 36, the beam is made to rotate at a synchronized, even submultiple frequency of that of tube 1. While the beam in tube 1 makes one rotation, that in tube 32 passes from one channel to the next. A blocking pulse generator 45 causes the beam in tube 1 to be cut off for a period during each rotation so that the pulses of one of the tube 1 channels are replaced by pulses from tube 32, which are also applied to lead 31. Alternatively, the appropriate aperture in plate 10 may be omitted. Demodulation is effected by means of the arrangement shown in Fig. 3. The input pulses are applied to valve 49, the output from which includes an open-circuited delay line 50. The time delay of line 50 is such that the reflected first pulse of the pair of closely-spaced synchronizing pulses is superimposed on the second pulse of the original wave, so that clipper circuit 51 operates and selects the synchronizing pulses. The output of clipper 51 is used to synchronize base-wave generator 58 which controls the rotation of the beam in tube 62, and, at the submultiple frequency, the rotation of the beam in tube 77, in the same manner as in Fig. 1. The incoming pulses are also applied to the grid of tube 62, to allow spurts of electrons to reach the targets 68 to 72, the amplitude of the output from each target electrode being proportional to the time displacement of the incoming pulse. Specifications 603,614 and 624,514 are referred to. The output from target 68 is applied to tube 77 and further subdivided between targets 78 to 82, corresponding to each of the low-frequency telegraph channels. The output from each of the targets 69 to 72 is applied to a low-pass filter 74 and utilization device 75. An alternative arrangement provides for the number of target electrodes in tube 77 to be correspondingly increased and for the frequency divider 84 feature to be omitted.