GB684574A - Improvements in or relating to cathode-ray tubes and circuits therefor - Google Patents

Abstract

684,574. Automatic exchange switches. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Dec. 16, 1947 [Oct. 23, 1946], No. 26249/50. Divided out of 684,552. Class 40 (iv). [Also in Groups XIX, XL (a) and XL (c)] In a circuit for a cathode-ray tube for use as a line selector or a group selector in an automatic telephone system, of the kind in which the beam can be stabilized in any one of a plurality of rest positions as described in the Specification 684,552, the beam is adapted to be deflected by two or more mutually inclined deflecting fields and its position is stabilized with respect to each of the fields in response to the effect thereon of beam current flowing through one or more collecting electrodes which is or are coupled therewith. Fig. 4 shows diagrammatically the construction of the collecting electrodes of a tube having three stable positions for the beam, each position lying at the centre of four collecting electrodes 98, 99, 100 and 101. The collecting electrodes are coupled as shown to a horizontal deflecting coil 103 and vertical deflecting coil 102 in such a way that if the beam wanders from the centre on to one of the collecting electrodes a restoring force in the direction of the arrow on the collecting electrode is applied by virtue of the beam current flowing through the collecting electrode to the appropriate deflecting coil. Electrostatic deflecting plates may be used instead of deflecting coils, Fig. 5 (not shown), and if two adjacent collecting electrodes in each set of four are secondary electron emissive then diagonally opposite electrodes may be connected to the same deflecting plate, Fig. 6 (not shown). The beam may be shifted from one stable position to another by pulses applied to the deflecting plates or coils. In Fig. 8 two sets of collecting electrodes are arranged in two circular arrays and a further collecting electrode 130 is arranged behind them. Electrodes 126I and 126II are connected to one horizontal deflecting plate and electrodes 127 to the other; the beam may thus be stabilized within either of the two areas bounded by these electrodes, and the other electrodes are similarly connected to the vertical deflecting plates so that the beam may be stabilized in any position within the area bounded by the collector electrodes. The outer ring of electrodes may be omitted and these may be six or twelve collector electrodes in the inner ring, Figs. 9 and 10 (not shown); the collector electrodes may be connected through a resistance network to electrostatic deflecting plates or may be connected to tappings on a deflection coil which may be wound similarly to the rotor winding of an electric motor. The electrodes may also be arranged as shown in Fig. 11 with stable positions at each re-entrant angle of the Figure, or as shown in Fig. 13. In Fig. 13 the beam may be shifted from one stable position 150 to another position 152 by means of a radial pulse towards the centre which causes the beam to impinge on electrode 151; the beam may be returned from position 152 to position 150 by an outward radial pulse.