GB442740A - Relaxation oscillation generator - Google Patents

Abstract

442,740. Valve generating circuits. RADIOAKT. - GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, Berlin. Aug. 14, 1934, Nos. 23443 and 23444. Convention dates, Aug. 14, 1933 and Aug. 21, 1933. [Classes 40 (iii) and 40 (v)] The relaxation oscillation generators for the image frequency and line frequency potentials of a cathode ray television system are similar in general arrangement but differ from each other in that the discharge period of the line frequency generator is at least equal to the duration of an image point while the grid circuit of the image frequency generator comprises an additional resistance 20, Fig. 2. In the line frequency oscillator, Fig. 1, the condenser 2 is charged through the circuit 3, 19, 4 ; the resistance 19 is included in the discharge circuit across the thyratron 1 in order to make the discharge time at least equal to or greater than the period of transmission of a single point. The ignition voltage of the tube 1 is raised by increasing the biassing resistance 4 to prevent increase in oscillation frequency due to the condenser 2 not fully discharging. The screen grid potential of the amplifier 9 is such that the exponential curvature of the potentials in circuit 3, 2 is compensated by opposite curvature of the characteristic of valve 9. The inner wall of the envelope of valve 9 has an earthed silver coating to prevent shift of the ignition point. The image frequency oscillator, Fig. 2, dispenses with resistance 19 of Fig. 1 and the grid circuit of the thyratron 1 includes a resistance 20 to prevent arcing at the grid. Synchronizing potentials are applied at terminal 6 in both oscillators and the output to the deflecting plates from terminal 15 should be constructed as a high pass filter.