GB553370A - Improved method of and means for the production of electric potential variations of triangular form - Google Patents

Abstract

553,370. Electron beam valves and circuits therefor. INTERNATIONAL TELEVISION CORPORATION, Ltd., NAGY, P., and GODDARD, M. J. June 13, 1941, No. 7539. [Classes 39 (i) and 40 (v)] A saw tooth wave generator comprises a beam tube with deflection plates arranged to cause the beam alternately to contact two target electrodes so as to alternately charge and discharge a capacity The capacity may be the deflection plates of a cathode ray oscillograph and a television signal having two periodic signal components established at different amplitude levels may be applied to the deflection plates. One of the target electrodes is charged positively by secondary emission while the other target electrode has associated with it a suppressor electrode and so is charged negatively. Fig. 7 shows a tube construction adapted to provide line and frame scanning potentials, electrodes XF, YF and XL, YL forming duplicate target electrodes with the lines of demarcation between positive and negative charging mutually displaced. The cathode B provides a line source of electrons which are focused by anodes A1, A2 and controlled by plates P1 ... P5, and impinge on either electrode XF or YF to charge output condenser COF. The charging is effected by secondary emission from electrode YF or by the electrons striking plate XF. Electrodes XL, YL similarly charge condenser COL under the control of the line synchronizing pulses. The beam does not reach electrode YF during the line pulses but only during the frame pulses to produce the sawtooth frame potential across condenser COF. Grids SF, SL prevent electrons leaving electrodes XF, XL when the potential is positive, which electrode E screens the electrodes YF, YL. An auxiliary electrode Q collects part of the secondary electrons emitted by electrode YL during synchronizing pulses to charge plate P3 to assist in the deflection of the beam to electrode YF during the longer frame pulses. In a modification, Fig. 6 (not shown), electrodes of different emissive properties are used to obtain appropriate charging rates to give the frame and line scanning. Fig. 4 shows an arrangement modified to show several waves of a signal on an oscillograph in that the deflection plates PI, P3 and the electrode E are connected to the second anode through resistance R2 and to the capacitive potentiometer C1, C2 joining plate P4 to electrodes XV. In this way the electrodes are progressively charged and the plate P3 acquires a negative potential so that the beam reaches the elecrode Y after a time interval depending on the value of variable capacity C2. Specification 553,403 is referred to. Reference has been directed by the Comptroller to Specification 539,661.