GB683461A - Improvements in or relating to cathode-ray tubes - Google Patents

Abstract

683,461. Automatic exchange systems. NAAMLOOZE VENNOOTSCHAP PHILIPS GLOEILAMPENFABRIEKEN. Nov. 24, 1947 [Nov. 27, 1946], No. 31048/47. Class 40 (iv). [Also in Group XL (a)] Cathode-ray tube apparatus for use in automatic telephony is of the kind in which an electron beam is moved continuously by deflecting means so that its point of impact on a target traces out a two-dimensional closed path and has the target formed as a collecting electrode which is continuous throughout the path or is divided into segments separatedby intervals which are narrower than the electron beam and coupled to the deflecting means through three or more avenues in such a way that when-the beam impinges on the collecting electrode the deflecting means are automatically caused to deflect the beam so that its point of impact on the collecting eleetrode moves continuously along the closed path. In the construction shown in Fig. 3 the collecting electrode is composed of separate segments 22 arranged in an annulus, the spacing between adjacent segments being narrower than the cathode-ray beam. Each segment 22 is connected to the junction point of two resistances 23, the resistances 23 being equal in number to the segments 22. and being connected in a ring, three or more points 26, 26a of which are connected to a source of positive potential through resistances 24 and to the deflecting plates 25, 25a, each deflecting plate being displaced more than 90 degrees from the corresponding point 26, 26a. The collecting electrode can be provided with further segments 29, 30 connected to the segment 22b and positioned partly behind the segments 22 and formed with recesses 29a at each interval between the segments 22 so that part of the beam can pass -through the gap between the segments. The segments 29, 30 tend to urge the beam inwardly and outwardly respectively. The segments 22 need not be spaced as shown but may be positioned one behind the other. The beam may follow any closed curved path. In the construction shown in Fig. 4 the beam is caused to follow one closed path 32, 33, 34, 35, &c. or another closed path 32, 33, 36, 37, &c. according to the strength of the beam current through the segment 33. Arrest of the beam can be effected in the arrangement shown in Fig. 3 by disconnecting a predetermined segment 22 from the ring of resistances 23 and connecting it to the diametrically opposite point in the ring. The direction of travel of the beam can be reversed if the segments of the collecting electrode have secondary emission properties and a grid carrying a suitable voltage for suppressing secondary emission is mounted in front of one' of them. Such an arrangement can be used in a a call.-finder for automatic telephone systems. In the construction shown in Fig. 7, the direction of travel of the beam is reversed at 46 with a suitable current strength and the beam comes to rest on the edges of the electrodes 50 and 46.