GB652361A - Improvements in and relating to pulse signalling systems - Google Patents

Abstract

652,361. Multiplex pulse signalling. GENERAL ELECTRIC CO., Ltd., and LEVY, M. M. Feb. 6, 1947, No. 3562. [Class 40 (v)] In a multi-channel pulse signalling system time-modulated pulses before demodulation or separated into individual channels are first broadened so that their leading or trailing edges occur at the instants of occurrence of predetermined points in the waveform of the pulses and their other edges at constant intervals. To prevent cross-modulation the pulses, before broadening, are separated into r groups of s channels by phase-displaced series of rectangular pulses of group recurrence frequency generated by an oscillator controlled from the signal synchronizing pulses and respectively applied to one grid of a valve at the same time as the pulses to be separated are applied to another grid, or, Fig. 11, by applying the pulses to a cathode-ray tube beam rotated over a series of r anodes A, the anodes becoming successively charged by secondary emission to an electrode E. The separated pulses then may be applied to the anode of a diode D<SP>3</SP> after the commencement of periodic pulses of constant width applied at T<SP>13</SP> across cathode resistance R<SP>3</SP>, width-modulated pulses resulting with edges coincident with the time-modulated pulses and trailing edge of the periodic pulses respectively. The pulses may finally be separated into individual channels by further multianode tubes connected to each anode and demodulated by low-pass filters. The pulses alternatively may be broadened as described in Specification 652,353, using damped tuned anode circuits, and width-modulated as in circuit C<SP>2</SP>, R2, D<SP>3</SP>, Fig. 11. The broadened pulses may be rendered rectangular, using the original periodic rectangular pulses and timemodulated pulses before broadening, Figs. 2 and 3, respectively (not shown). In. Fig. 14 broadened pulses without reshaping are applied at T<SP>19</SP> to the grid of a cathode-ray tube having an apertured plate AP through which a circularly-swept beam impinges on collector anodes A. The modulated leading edge of each pulse occurs when the beam is on an anode A, the fixed trailing edge being determined by the aperture edge. Feed-back by way of valves V<SP>9</SP>, V<SP>8</SP> from the plate AP to the grid ensures the fixed edges being sharp and super-imposing of the original time-modulated pulses on the cathode at T<SP>21</SP> renders the modulated edge sharp. Alternatively, unbroadened pulses may be applied at T<SP>19</SP> to the grid by way of a diode D4, Fig. 16, the condenser C3 quickly charging to produce a pulse persisting till the plate AP by collecting electrons reduces at T<SP>20</SP> the grid potential of a valve V<SP>10</SP>, and renders conducting a diode D<SP>5</SP> shunting the condenser. The coupled valves may alternatively form a multivibrator or be gas-triggered. To synchronize the beam one of the collector anodes may be split into two segments each connected by amplifying valves to a relay to rotate either of two ways a motor connected to a generator of two oscillations in phase quadrature supplying the beam deflecting coils, the motor operating to vary the relative phase of the oscillations to restore equal or no collection of current at the segments at the instant of the signal synchronizing pulse. Specification 587,942 also is referred to.