GB727533A - Circuit arrangements for limiting testing time of selectors in telecommunication installations - Google Patents

Abstract

727,533. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES. March 16, 1953 [March 14, 1952; March 14, 1952], No. 7235/53. Class 40 (4). In a system in which a selector is stopped on an idle outlet when a discharge tube conducts, the discharge tube is enabled by a potential applied momentarily under the control of the selector or its driving mechanism when the selector reaches each outlet and at a time such that a successful test at one outlet cannot be too late to prevent the selector moving to the next. In a selector RW similar to that described in Specification 712,013, in which the outlets are characterised by different recurring series of pulses P1, P2, P3 and the pulses are connected to the grids G1, G2 of the gas discharge tube RO1 over a digit switch MW and a control wiper d of the selector respectively, the application of the potential denoting an idle outlet to the cathode together with the simultaneous presence of pulses at the grids G1, G2 is not sufficient to fire the tube RO1. The selector RW is driven alternately by two magnets M1I, M2I connected up by contacts m1 m2 actuated at each step. The energization of one of the magnets momentarily induces a potential across its second winding M1II, M2II which is applied to grid G1 and enables the discharge tube RO1 which if the selector is at an idle wanted outlet fires. The rise in potential of the outlet connected to wiper c as a result of RO1 passing current busies the outlet. Discharge tube RO2 ignites to bring up P which energizes both magnets M1I, M2I to stop the selector and earths wiper c to finally seize the outlet. In a modification the windings of the switch magnets providing the enabling potential are connected between the cathode of discharge tube RO1 and wiper c. In a further modification the magnets have one winding only and the energizing circuits of the magnets are connected over condensers to a third grid of the discharge tube RO1 to provide the enabling potential. Instead of deriving the enabling potential from the magnets, the potential may be applied over contacts operated by movement of the selector.