GB458161A - Improvements in or relating to television systems - Google Patents

Abstract

458,161. Automatic control systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London.-(Assignees of Bedford, A. V. ; 118, East Palmer Avenue, Collingswood, New Jersey, U.S.A.) June 11, 1935, No. 16872. Convention date, June 9, 1934. [Class 38 (iv)] [See also Group XL] Oscillation frequency.-In television, the line and frame frequency oscillations are derived from a common oscillator which is controlled by the phase relationship between the frame oscillation and an A.C. mains supply, so as to maintain a predetermined frequency and phase relationship with the A.C. mains supply. The A.C. mains supply also drives the film so that the scanning is correlated with the movement of the film. A blocking oscillator 15, Fig. 1, feeds a chain of similar oscillators 41, 43, 45, 47, each tuned to a sub-multiple of the oscillator 15 to produce oscillations of frequency 48 which control a sawtooth wave form generator 49 for controlling the slower deflection of the cathode ray beam. A similar generator 51, fed from the generator 15, controls the line frequency oscillation generator 53. The film 55 is intermittently driven by gearing from a motor 63 energized by the 60 c /sec. A.C. from the mains supply. The oscillator 47 feeds an oscillator 89 to produce a frequency equal to that produced by subdividing the mains frequency at 95. These two oscillations are then applied through wave shaping circuits 91, 97 to the input of a correcting circuit 71. This circuit comprises a valve 75 acting as a distorting amplifier or detector so that the current in the resistance 27 depends on the degree to which the two frequencies are out of phase. This current flow is used to bias the oscillator 15 to control its frequency.