GB205472A - Improvements in or relating to wireless electric signalling systems - Google Patents

Abstract

205,472. Compagnie pour la Fabrication des Compteurs et Materiel d' Usines Ó Gaz, (Assignees of Soc. des Etablissements Ducretet). Oct. 14, 1922, [Convention date]. Thermionic amplifiers and detectors.-Noises due to using rectified alternating current to supply the plates, and alternating current for heating the filaments, are eliminated by introducing into the plate circuits a second source of alternating current of the same frequency as the supply. A differential arrangement of two valves which causes the undesired currents to be balanced out may be used in combination with this method. As shown, the filaments of valves 1, 1<a> are fed from a transformer 6 and the plates are fed with rectified currents from the points 5, 5. Feed noises are partially eliminated by the additional winding 10 on transformer 6 in the plate circuits. The input transformer 17 has two secondary windings so arranged that when signal currents make the grid 3 positive they make the grid 3<a> negative. The output transformer has two primaries 20, 20a arranged so that currents in the same direction through them produce no effect in the secondary 21. Fluctuations due to feed' currents do not therefore affect the telephone 9. The effects of signals on the other hand are added in the secondary 21 since they are 180‹ apart in phase. In the case of a high-frequency system in which' the last valve is a detector the final output transformer has an additional primary winding through which flows only the plate current of one of the preceding high-frequency valves.