GB737156A - Improvement in or relating to colour television systems - Google Patents

Abstract

737,156. Colour television systems. RADIOINDUSTRIE. Nov. 12, 1953 [Nov. 19, 1952], No. 31423/53. Class 40 (3). [Also in Group XL (c)] In a sequential colour television system synchronizing of the colour sequence is effected by adding to synchronizing pulse b2 occurring before one colour frame or line additional pulses b1, b3, b4, the effect of which is momentarily to increase the pulse repetition frequency. To produce from this a colour synchronizing pulse the complete television synchronizing signal is fed to a differentiating circuit C1, R1 to separate the frame pulses from the line pulses and the former are applied via a clipper valve V to the frame scanning generator. The frame pulses are also applied to the grid of a normally non- conducting valve V1<SP>1</SP>. A pulse derived from the frame coils B1, B2 during the fly-back is applied through a lengthening and delaying circuit R3, C3 to the normally negative screengrid of valve V1<SP>1</SP> to render it conductive when a pulse occurs on the control grid. Accordingly an output pulse occurs at the anode only when the further pulses follow the normal frame pulse. In an alternative arrangement valve V1<SP>1</SP> is omitted and the valve V1 is replaced by one having two control grids, capacitor C3 being connected to the second control grid. Current flows to the latter grid to produce a colour synchronizing pulse only when there is a control grid pulse to coincide with the screen grid pulse.