GB559005A - Improvements in and relating to television transmission - Google Patents

Abstract

559,005. Television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Sept 11, 1942, No. 12858. Convention date, Jan. 31, 1941. [Class 40 (iii)] Disturbing effects of pulses 42, Fig. 2, produced by periodical illumination of screen 14, Fig. 1, of transmitter tube 10, are prevented by triggering off a D.C. reinserter 31 during the period of these pulses. In the arrangement shown, the transmitter tube 10 is a low-velocity tube, for example as described in Specification 540,281, with a scanning control electrode 11 supplied with synchronizing pulses from a generator 12 of synchronizing and blanking pulses. The images are projected on the screen 14 of the tube from a film 46 driven intermittently by a mechanism 45 as described in U.S.A. Specification 2,082,093. This mechanism is operated by a synchronous motor 49 supplied from the source 51, which also supplies the synchronizing-pulse generator 12. The signals produced by the tube 10 are amplified by the chain of valves 21, 22, 26. A triode 31 is connected to the grid of amplifier 26 and co-operates with the condenser 36 and the resistance 37 to reinsert D.C. into the signal as described in U.S.A. Specification 2,194,514. The grid of the triode 31 is connected to a keying-pulse generator 53 synchronized by blanking pulses from the synchronizing-pulse generator 12. The keying-pulses 54 produced by the generator 53 trigger-off the triode 31 during the period of the pulses 42. Blanking pulses, Fig. 3, are fed into the amplifying chain through a switch 57.