GB610910A - Improvements in or relating to apparatus incorporating a cathode ray device, particularly television receivers - Google Patents

Abstract

610,910. Television. LAWSON, D. I., and PYE, Ltd. April 9, 1946, No. 10851. [Class 40 (iii)] In a cathode-ray device in which the electron beam is deflected by a deflecting coil, the amplitude of the deflection is varied by varying the number of effective turns on the deflecting coil by a switching means which simultaneously varies the value of an inductance connected in series with the deflecting coil such that the total inductance of the circuit remains substantially constant for different positions of th e switch. As shown in the drawing, the. line deflecting coil 1 which is fed from the line transformer 2 connected in the output circuit of the line amplifier or oscillator valve 3 is provided with a series of tappings a, b, c and is connected in series with an inductance 4 which is also provided with a series of tappings a<1>, b<1>, c<1>. A switch 5 is provided for interconnecting tapping points of the line deflecting coil and of the inductance 4, the arrangement being such that as the number of turns on the deflecting coil which are effective to produce deflection of the cathode-ray beam is reduced, by changing the position of the switch, the number of turns of the inductance 4 which are connected in series with the deflecting coil is simultaneously increased, and vice versa, thus maintaining the total inductance of the circuit substantially constant at different positions of the switch. It is stated that the invention is particularly applicable in arrangements in which the high voltage supply for the cathode-ray tube is derived from the line oscillator of the apparatus, for example, through the rectifier 6.