GB653878A - Improvements in or relating to electronic switches - Google Patents

Abstract

653,878. Discharge apparatus. GENERAL ELECTRIC CO., Ltd., HEAD, N. E., and KAYE, E. J. Aug. 20, 1948, No. 22043. [Class 39 (i)] An electronic switch particularly for use in multichannel signalling systems comprises an evacuated envelope 1 containing an axial cathode 2, a plurality of anodes 3 shaped to form a discontinuous cylinder concentric with the cathode and auxiliary electrodes or guides 4 extending radially from the vicinity of the cathode towards the gaps 8 between the anodes 3.' The anodes 3 are connected in series with respective load resistors 7 of a value such that anode potential does not fall appreciably when anode current flows, but the commoned load resistors 9 are such that the potential of an associated guide 4 falls substantially upon current flow therethrough. The tube is subjected to a uniform axial magnetic field such that electrons emitted from the cathode move in circles which drift along equipotential lines produced by the electric field and initially no anode current flows. If now one of the anodes is reduced to cathode potential, the equipotential lines of near cathode potential will be displaced towards that anode, resulting in emitted electrons being collected thereby and one or other of the adjacent guides 4, whereupon the potential of the current carrying guide drops so that even if the low potential anode is restored to its normal positive potential electrons still continue to flow to the anode and operative adjacent guide. These conditions persist until the potential of another anode is reduced below that of the guide 4 in which current is flowing, when the electron flow is switched to the other anode and an adjacent guide. The electron flow is thus switched from one anode to another by applying a negative pulse to the anode to which the flow is to be switched. Two such switches used, respectively, at the transmitter and receiver ends of a multi-channel signalling system may be synchronously stepped by applying negative pulses simultaneously thereto. Switching may, alternatively, be achieved by pulsing the guides. The electron flow to the various anodes may be modulated by means of a common concentric grid or by individual grids in the respective cathode-anode paths. Specification 619,785 is referred to.