GB643155A - Television receiver - Google Patents

Abstract

643,155. Television. BENDIX AVIATION CORPORATION. April 17, 1947, No. 10282. Convention, date, May 31, 1946. [Class 40 (iii)] A contrast control and video gain circuit arrangement for television receivers comprises a video amplifier stage provided with an output load impedance, across which the control electrodes of a cathode-ray picture reproducing tube are directly connected, and an input circuit including a variable resistor so connected that variations of the resistance simultaneously vary the amplitude of the video signals and the magnitude of the bias on the control electrodes of the video amplifier stage. In the arrangement shown in Fig. 1, the control electrodes 21, 23 of the cathode-ray tube are directly connected across the load impedance 20 of video amplifier 15, the input circuit of which includes a pre-set resistor 17 which is so adjusted that variation of the video gain control 16 changes both the level of the video signals and the D.C. voltage drop across impedance 20 such that optimum contrast conditions exist for all levels of video signal The Specification as open to inspection under Sect. 91 describes a modification (Fig. 2, Cancelled, not shown) in which the arrangement of Fig. 1 is conductively connected to the second detector of a television receiver in order. to preserve the D.C. component which, in the arrangement of Fig. 1, is lost by passage through the coupling condenser 13. This subject-matter does not appear in the Specification as accepted.