GB439818A - Improvements in or relating to means for superposing currents of musical or high frequencies on electrical distribution networks for signalling or for telecontrol - Google Patents

Abstract

439,818. Signalling overpower circuits. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIAL D'USINES A GAZ, 12, Place des Etats-Unis, Montrouge, Seine, France. June 15, 1934, No. 17768. Convention date, June 22, 1933. [Class 40 (i)] Signalling or control currents of musical or high frequencies are generated by a dynamoelectric machine and superposed on an electrical distribution network by electronic tubes (vacuum tubes, mercury vapour tubes, &c.) Single or polyphase currents may be used. In the arrangement shown, a three-phase generator A has each phase connected to the grid of a triode 4 the output circuit of which is connected by step down transformers 5, 3 to the feeders 2. Condensers 6 are inserted to provide a reactive component and to block the supply frequency. The condensers may be variable to time the circuits to the frequency of the signalling currents, or the circuits may be damped to respond to the whole range of signalling frequencies. In modifications, the transformers 5 may be replaced by impedances capacity-coupled to the primaries of transformers 3 ; or the secondaries of transformers 5 may be connected in series with condensers to the feeders, the transformers 3 being dispensed with. The signalling frequency is varied by control of the generator and any particular frequency may be slightly varied in order to ensure response of all the desired receivers which may vary slightly as regards frequency response. The signalling currents may be modulated at a lower frequency by modulating the field current of the generator. Specification 281,275, [Class 40 (i)], is referred to.