GB553851A - Television scanning system - Google Patents

Abstract

553,851. Television; valve oscillators. HAZELTINE CORPORATION. April 25, 1942, No. 5575. Convention date, July 1, 1941. [Classes 40 (iii) and 40 (v)] The saw-tooth voltages controlling the scanning operation of the cathode-ray tube of a television receiver are utilized also to control the relative amplitudes of the oscillators generating the saw-tooth voltages and this has the effect that the manual adjustment of one generator causes automatically a corresponding adjustment of the other to maintain the aspect of ratio of the picture. As shown in Fig. 1, the line and field scanning saw-tooth voltages are produced by the oscillators 18, 19 respectively, and are fed to the scanning coils 21, 23, in series with which, resistances 25, 26 are inserted. The saw-tooth voltages developed across these resistances are fed through differentiating circuits 40, 43 and diodes 41, 44 to condensers 42, 42<SP>1</SP>, producing therein pulses E, F, one of which is inverted. These pulsations are fed through filter circuits 46, 47, 48 and 461, 47<SP>1</SP>, 481 to the two grids of a double-triode 45, the anode circuit of which includes the anode resistance 33 of the valve 27 of the oscillator 18. By this arrangement, variations of scanning saw-tooth voltages appearing at the resistances 25, 26, produce opposite changes in the impedance of the double-triode 45 which causes corresponding variations of the voltages applied to the oscillator valve 27 and therefore of the amplitude output of said oscillator. The other oscillator 19 is provided with a variable anode resistance 331 for manual adjustments. The filter circuits 46, 47, 48 and 46<SP>1</SP>, 471, 481 may be made fast or slow acting as desired. The differentiating circuits 40, 43 with diodes 41, 44 may be replaced by peak rectifiers.