GB676968A - Improvements in circuits for cathode-ray tubes - Google Patents

Abstract

676,968. Cathode-ray tubes. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. March 11, 1949 [March 16, 1948], No. 6739/49. Class 39 (i). [Also in Group XL (b)] In a cathode-ray tube in which the beam is deflected over a group of targets 5, 6, 7, 8, Fig. 1, an auxiliary electrode 9 is connected by a feed-back path including condenser 16 to the deflecting plate 3, so that the angular speed of deflection of the beam during the time it strikes electrode 9 is different from the angular speed while it is striking electrodes 5, 6, 7, 8. The normal deflecting voltage is supplied by saw-tooth generator 14 via resistance 13, and deflector plate 3 is earthed via resistance 11 and battery 12. A condenser 16a, which may be variable, is connected in parallel with the resistance 11. The beam initially rests on target 5 and is deflected to the right as the saw-tooth voltage increases linearly. When the beam strikes electrode 9, the voltage drop across resistance 10 is transmitted to deflecting plate 3 so that the angular speed of deflection is increased. The arrangement may be a multiplex distributer, the time the beam takes in passing between the target electrodes 5, 6, 7, 8, thus being reduced. The variation of the resultant deflecting voltage with time depends on the time constant of the circuit comprising deflecting system 3, 4, condensers 16, 16a, and resistance 11. In an alternative method of operation, the generator 14 supplies a positive voltage pulse so that the beam is moved over to target 8. The voltage then decreases exponentially and the beam in its return path moves more slowly each time it strikes electrode 9. Compared with its angular velocity over targets 8, 7, 6, 5. In a modified construction, Fig. 3 (not shown), the additional target electrode is apertured and is arranged in front of the group of targets. If the feed-back path is connected to deflecting electrode 4 instead of to electrode 3, the beam will move more slowly when it strikes electrode 9 and faster over electrodes 5, 6, 7, 8, and this is also true in the arrangement of Fig. 3. A similar result is achieved by making the additional target electrode secondary emissive.