GB573405A - Electrical control system - Google Patents

Abstract

573,405. Electric control systems. STANDARD TELEPHONES & CABLES, Ltd. July 2, 1943, No. 10767. Convention date, Sept. 14, 1942. [Class 40 (i)] [Also in Groups XXXIX and XL] Two thermionic tubes A1, G1, A2, G2, which may have the same envelope and may.have the same or different characteristics are associated with means for applying various voltages to their grids through high resistances R4, R5 and further means for varying a common voltage applied to their cathode or cathodes, the arrangement being such that for any particular pair of grid voltages, only one cathode voltage causes their anode currents to differ by an effective amount. Alternatively the common voltage may be applied to the grids and the various voltages to the cathodes. The anode currents may feed the respective windings of a differential relay or, as shown, may produce voltages which are applied to the respective control electrodes, e.g. CE1, CE2, of a gasfilled discharge tube of hot or cold-cathode type. In the arrangement shown in Fig. 1, the cathode voltage is varied by a selector switch the driving circuit of which is opened by a relay in the main discharge path of a coldcathode tube GV. In a modification, Fig. 3 (not shown), the tubes have different characteristics and the same adjustable voltage may be applied to both the grids. Alternatively, the voltages may differ by a constant amount In a modification, Fig. 5 (not shown), a twin tube and a gas-filled tube, as shown in Fig. 1, are provided for each of a number of control operations, the grids of the tubes being separately biassed and the cathodes connected together and to an adjustable source of potential by which a break down may be caused in any of the gas filled tubes according to the potential selected. In an automatic exchange system, Fig. 6, a digit register controls the respective potentials of the grids of a twin tube like that shown in Fig. 1 and a group selector hunts for a cathode potential that will cause a breakdown of GV and consequent operation of a stopping relay GVR. In other arrangements, Figs. 7 and 8 (not shown), the double tube is coupled to the gas-filled tube with the aid of ordinary and differential transformers. The system may be applied inter alia to the control of lifts, calculating machines and telegraph or ticket printers.