GB447403A - Improvements in or relating to television and like systems - Google Patents

Abstract

447,403. Television. ELECTRIC & MUSICAL INDUSTRIES, Ltd., Blyth Road, Hayes, Middlesex, and MANIFOLD, M. BOWMAN-, Heathcot, Worplesdon Station, Surrey. Oct. 16, 1934, No. 29596. Addition to 392,383. [Class 40 (iii)] A solenoid deflecting a cathode ray has a " black-out " circuit in parallel, the time constants of the deflecting and " black-out " circuits being such that the black-out " circuit develops, the first differential of the deflecting current which is applied to suppress the cathode ray during the return lines. The output of the frame oscillator is fed to the grid of pentode 5 to energize the deflecting solenoid 11. A " black-out circuit comprising condenser 12, resistances 13, 14 and biassing resistance 15 develops the first differential of the deflecting current which is applied to the tube 1. It is shown that the time constants of the " black-out" " and deflecting circuits must be equal if the voltage applied to the tube 1 is to have no components other than the first differential of the deflecting current. The resistance 8 provides negative feed-back to improve the wave-form of the deflecting current and may be replaced by (1) a coil coupled to the solenoid 11 and connected between grid and cathode of valve 5 ; (2) a potentiometer in series with the solenoid 11, a tapping being connected to the grid of valve 5 over a condenser, Fig. 2 (not shown) ; or (3) a variable resistance connected at one end to the cathode over a condenser, condenser 10 being omitted, and at the other end to the solenoid 11, Fig. 3 (not shown). The resistances 13, 14 may be replaced by a potentiometer, Fig. 2 (not shown). The solenoid 11 may be transformer coupled to the output of valve 5, Fig. 3 (not shown). A similar circuit is associated with the line oscillator, Fig. 3 (not shown).