GB638897A - Improvements in and relating to electric pulse signalling systems - Google Patents

Abstract

638,897. Cathode-ray tubes. GENERAL ELECTRIC CO., Ltd., FARREN, L. I., HEAD, N. E., and LEVY, M. M. Feb. 4, 1948, No. 3276. [Class 39 (i)] [Also in Group XL (c)] A cathode-ray tube pulse generator and time modulator comprises means for deflecting the beam along a path passing recurrently over or close to a slot or strip electrode, means for deflecting the beam transversely with respect to said path and means to deflect the beam by the modulating signal to vary the point along the slot or strip at which the beam crosses it. In a multichannel arrangement, the beam describes a zig-zag'path crossing a plurality of slots or strips in succession. Thus two of the slots or strips 16, Fig. 2, are scanned by the beam which traces out a path 21 in the absence of modulation, the signal being used to deflect the path between limits 23, 24 and pulses being generated when the beam passes over the slots or strips. In one embodiment, the beam from gun 10, 11, Fig. 3, is swept by deflecting coils 12, 13 in a circular path over a plate 15 having a number of equally-spaced arcuate slots 16. The modulating signal is applied to a deflecting plate 18 of which one is provided corresponding to each slot while to the common deflecting electrode 17, in the form of a frusto-conical surface, is applied a symmetrical saw-tooth voltage derived by providing a further apertured plate 28, the apertures 29 in which are larger than the slots 16, Fig. 4, and the potential of which varies in square wave form (a). Fig. 5, as the beam traverses it. An integrating circuit 32 converts the wave form (a) to a sawtooth (b) which is amplified at 33 and fed to electrode 17. Negative output pulses are derived from target 25 arranged behind the slots or positive pulses from plate 15. The slots may be disposed so that their longitudinal centre lines are at some angle to the circle forming the centre line of the zig-zag. Radial screens are preferably introduced between the individual modulating electrodes 18 and also transverse screens 34, 35 having apertures 36, 37 respectively. In another embodiment three slots 16, Fig. 6, are arranged for operation with rectilinear motion of the scanning beam. A saw-tooth oscillation applied between electrodes 38, 39 deflects the beam slowly from left to right and rapidly from right to left, while a symmetrical saw-tooth oscillation of three times the frequency is applied to the interconnected electrodes 18. The path of the beam is hence slowly over the path 40 from left to right and rapidly over the return path 41. The slots 16 and apertures 29, 37 are of the relative shapes shown and screens 42 are disposed between adjacent modulating electrodes 17. The symmetrical saw-tooth scanning waveform is derived from the electrode with apertures 29.