GB652402A - Improvements in and relating to pulse signalling systems - Google Patents

Abstract

652,402. Cathode-ray tubes. GENERAL ELECTRIC CO., Ltd., and LEVY, M. M. Aug. 19, 1948, No. 21919. [Class 39 (i)] [Also in Group XL (c)] In a modulator for producing time or duration modulated pulses, using the multichannel cathode-ray tube distributer and time modulator described in Specification 652,397, the signal voltages from six channels are applied respectively to deflection plates M1 ... M6, Fig. 1, and the waveform (d), Fig. 3, is applied to the opposite common deflecting electrode M. The beam is thus scanned across the channel pulse producing slots or plates S1 ... S6 in non-linear fashion, crossing them at a time dependent also upon the signal amplitude. Horizontal scanning is produced by waveform (f), applied to plates E1, E2, and derived by the summation of saw-tooth waveforms (b), (c), and the beam is suppressed between the vertical strokes by applying waveform (a) to the control grid or waveform (e) to the cathode. Alternatively, a modulator of the type in which pulses having sloping tops are applied with the signal voltage to a clipper circuit, may be used, the sloping tops of the pulses being made non-rectilinear and of the form shown in Fig. 3 (d), the slope of the pulse being a minimum at the centre of the pulse. In one receiver, using the multichannel cathoderay distributer and demodulator described in Specification 652,400, and applicable to duration modulated pulses into which time modulated pulses are first converted, the rotating beam is deflected radially by electrodes 21, 22, Fig. 8, to which the pulses are applied. The bucketshaped anodes 20 provide channel outputs of amplitude modulated pulses. The amplitude expansion is produced by varying the intensity of the beam as it sweeps across the anode by applying a voltage waveform 26, 27, Fig. 9, to one control grid. In another embodiment, the intensity of secondary emission from plate anodes is varied by providing a collector electrode to which is applied a voltage waveform, which is the inverse of 26, 27, Fig. 9, during the passage of the beam across an anode. Alternatively, bucket anodes with -a convex base 29, Fig. 11, facing the beam direction 30 provide for a secondary emission loss which is greater from the centre of the anode than on either side of this position. In a further embodiment, individual channel radial deflecting electrodes 31, Fig. 12, co-operate with a common electrode 32 to which is applied the voltage waveform of Fig. 13, which sweeps the beam over a pair of anodes 20, 20<SP>1</SP>, provided for each channel. The incoming time modulated pulses are applied to control the beam intensity and the anodes 20, 201 are connected to a push-pull amplifier 33. The amplifier output is fed back to the deflector electrode 31 in such phase that the beam is urged into the space between the two anodes 20, 20<SP>1</SP>. The voltage fed back consists of amplitude modulated pulses in which the signal has received expansion according to the law of the voltage waveform applied to electrode 32 and which are taken from the output terminal 35. Reference has been directed by the Comptroller to Specification 650,886, [Group XL (c)].