Patent GB-658734-A (GB)
Title: Improvements in and relating to the monitoring of multi-channel pulse signalling systems
Inventor: LEVY MAURICE MOISE
IPC: H04J3/00
Filed: 1947-05-08
Abstract: 658,734. Monitoring multiplex pulse signalling systems. GENERAL ELECTRIC CO., Ltd. May 8, 1947, No. 12489. [Classes 40 (v) and 40 (vi)] Monitoring means for a multi-channel pulse signalling system, consists of one or more cathode-ray tubes to which two scanning voltages of recurrent waveform are applied, the waveforms being relatively displaced in time and having a recurrence frequency equal to, or a multiple or submultiple of the channel pulse recurrence frequency. The channel pulses displace the ray or rays in a direction transverse to the scanning deflections. The display for a 100-channel system is described, being presented in the form of five parallel scanning lines on each of two tubes C1, C2, Fig. 2, one presenting channels 1 to 10, 21 to 30, &c., and the other 11 to 20, 31 to 40, &c. as shown numerically. For generating the scanning waveforms the synchronizing pulses of the system control an oscillator generating waveform (a), Fig. 1. A rectangular waveform (b) is obtained from (a) by frequency multiplication by a factor of five. The addition of waveforms (a) and (b) gives waveform (c) and their subtraction gives waveform (d). The leading edges L1 and L2 of waveforms (c) and (d) respectively, synchronize saw-tooth oscillators producing the full-line and dotted-line waveforms (e) respectively. The symmetrical triangular wave (f) is generated by multi-vibrator under the control of waveform (b) and by subtracting this triangular wave from those at (e), the full-line and dotted-line stepped waveforms (g) are obtained. The waveforms (g) are applied to the Y-plates of tubes C1, C2, respectively, and waveform (f) to their X-plates but in opposite senses to the two tubes. The beams are blacked out during even and odd half-cycles, respectively, of the wave (b) by applying it to the cathode and control electrode, respectively, of the tubes, and the channel pulses are applied to both sets of X-plates and may also control the beam brightness by application to the control electrodes. To emphasise one group of ten channels, the waveform (h) of adjustable phase may be applied to displace and/or brighten the corresponding scanning line. To examine one channel pulse or a small group, the waveform (i) of adjustable phase and duration may be used instead of (h), which, as shown, raises the base line of pulses 23 ... 25. A third tube C3 may display these pulses by using (i) as a brightening pulse and (j) as the time base waveform. The waveform (k) enables the position of the pulses in their channels to be displayed. One half-cycle of this wave corresponds to one channel width and presentations such as (a), (b), Fig. 3, may be obtained. A single cathode-ray tube may be used with two settings made available by switching, and giving the two displays of C1, C2, Fig. 2, alternatively. In a further modification, using a single tube, a saw-tooth wave having a working stroke nine channels in duration and a flyback of one channel duration, is applied to the X-plates. To the Y-plates are applied, by switching, either of the waveforms (e) or waveforms similar to (g) obtained by subtraction of the X-plate waveform from (e). Return trace black-out potentials are derived by differentiation of the scanning waveforms. In one switch setting pulses 1 to 89 excluding 10, 20, 30, &c. are displayed and, in the other, pulses 11 to 99, with the same channels excluded. The excluded pulses are displayed by changing the phase of the X-plate scanning potential in both switch positions. Specification 652,357 is referred to.