GB553403A - Improvements in or relating to electron discharge devices for the production of trapezoidal or saw tooth potential variations - Google Patents

Abstract

553,403. Cathode-ray tubes. INTERNATIONAL TELEVISION CORPORATION, Ltd., NAGY, P., and GODDARD, M. J. June 13, 1941, No. 5234/43. Divided out of 553,370. [Class 39 (i)] A beam deflection valve for the production of trapezoidal or saw-toothed potential variations, compries two output electrode systems X, Y, X1, Y1, which have a secondary electron emission co-efficient greater than unity. Coacting with these electrodes are collecting electrodes E, E1 and a suppressor grid S. The capacity CO in which a varying potential difference is built up about a fixed mean potential, as for example the deflection plates in a cathode-ray tube for line scanning, is connected between the electrodes X, Y1. As the strip beam from the cathode C, and first and second anodes A1, A2 is deflected across the electrodes by the signals applied electromagnetically or electrostatically between the plates PI, P2, the electrode X becomes progressively negatively charged by the beam as secondary emission is suppressed by the grid S, while Y1 becomes positively charged by secondary emission which is collected by the collector E1. At the end of a line, the beam impinges on the part Y of the electrode XY which is then discharged by secondary emission which is collected by the electrode E, while Y1 is discharged by secondary emission from X1, the grid S1 preventing the secondary emission from reaching the electrodes E1, E. The degree of charging the electrodes is varied by shifting the position of the beam by suitable potentials applied to pairs of plates P3, P4, P5. In a modification for line and frame scanning, Fig. 2, two similar electrodes XL, YL and XF, YF with suppressor grids SL, SF and a common collector electrode E are used, and are displaced laterally relatively to the path of the beam. An auxiliary electrode Q is connected to the plate P3 through a resistance R3. The parts XL, XF produce the line and frame scanning potentials. During each line synchronizing pulse, the electron beam is deflected to fall on the positive charging electrode XL producing the fly-back of the line deflection, but the deflection necessary to reach the YF is produced only by the longer frame synchronizing pulses. The rate of charging XF is slower than that of XL, and is effected by making the area in contact with the beam less or the capacity C.O.F. greater than C.O.L. Specification 553,370 is referred to.