Patent GB-675465-A (GB)
Title: Improvements in or relating to electron discharge apparatus
IPC: H01J21/14
Filed: 1946-03-06
Abstract: 675,465. Automatic exchange switches. ALFVEN, H. O. G., and ROMANUS, H. A. R. March 6, 1946 [March 7, 1945; Oct. 3, 1945; Feb. 25, 1946], Nos. 7035/46, 7036/46 and 7037/46. Class 40 (iv). [Also in Groups XL (a), XL (b) and XL (c)] An electron discharge apparatus for switching applications in telephone circuits utilizes a beam made up of electrons travelling in trochoidal paths under the influence of a main magnetic field transverse to the beam and a main electric field crossed in relation to the main magnetic field, the direction of the beam being controlled by (a) altering the distribution and magnitude of the electric field, (b) similarly altering the magnetic field, (c) varying the potential of the electron source, (d) altering the superimposition of the electric field on the magnetic field; or two or more of these methods together. It is shown that, for a magnetic field of sufficient strength, the beam follows approximately that equipotential line of the electric field which corresponds to the potential of the source. In one form, a number of collector electrodes 5a, 5b, 5c, Fig. 9, are arranged opposite a field electrode 3, and the potentials of these electrodes are adjusted so that the beam from cathode 1 follows the path 23. If now the potential of, say, 5c is lowered to that of path 23, the beam will be diverted to 5c ; but preferably the diverting function is given to separate diverting electrodes 6a, 6b, 6c placed between electrodes 5, which then act as passive output electrodes. Control electrodes may be placed in front of electrodes 5. Simple switching applications are described (see Group XL (a)), but in the application to a two-dimensional selector a first set of diverting electrodes 7, Fig. 14, cause the beam to enter the desired sub-group of electrodes in which the energized one 6a of a second set of diverting electrodes causes the beam to impinge on the desired output electrode 5a. A number of such twodimensional assemblies may be arranged about a single cathode, Fig. 15 (not shown), or built up into a three or more dimensioned assembly. In another form, the beam may be used to connect any one of a set of perforated electrodes 5, Fig. 17, to any one of a further set of electrodes 51, by suitable energization of diverting electrodes 6, 61. In an example of method (b), localized sets of long magnetic coils 26, 27, Fig. 22, are arranged at right-angles, in addition to the main magnetic field. Energization of coil 27a causes the beam to proceed up the desired vertical channel, where it is diverted to electrode 5a by energization of appropriate coil 26a. The trochoidal beam may be displaced at certain places in the direction of the magnetic field, for example by plates 13, 14, Fig. 25, in a twodimensional selector. Physical movement of the tube, for example by pivoting about the cathode, may be used to cause the beam, which remains fixed in space with the magnetic field, to fall on different targets. The output signal may be obtained by the magnetic or electric induction effect of the beam, Fig. 29 (not shown). The output system may comprise a plurality of electrodes, such as a pentode system of screens al, a3, Fig. 33, control electrode a2, suppressor a4 and output anode a5; these may be used for separate functions such as modulating, busymarking, or call-metering, or the output may be a secondary-emission current between two of them. By putting appropriate resistances in the output circuits, so that the collected beam current causes the collecting electrode to drop in potential, it may be arranged that the beam is held on that electrode after the diverting signal (which may be a short pulse) has passed; or by still further increasing the potential drop, the beam may be passed from one electrode to the next automatically until stopped at a marked electrode. This may be applied to simple switches, Figs. 34, 35, 38 (not shown), or to selectors in two or more dimensions. Where the normal potential of the collector is below that of the beam, the resistance must be negative, and circuits simulating this in a glow tube and a back-coupled thermionic valve are described, Figs. 36, 37, respectively (not shown). In a combined multiple finder and selector the various sets of electrodes such as finders A, B, Fig. 39, and selectors F, G are arranged in layers with corresponding electrodes interconnected. When there is no call, the beam passes cyclically over all the contacts as described above. Upon a call from a subscriber, say a1, the potential of the corresponding contact is raised and the beam stops there, as shown at B. Auxiliary mechanism then lowers the potential of the source and this, together with the drop in resistance Z5, secures that no other finder can stop at that electrode and also busy-marks the corresponding contact in all selectors, as is a14 in layer G. Specification 530,409, [Group XL], is referred to.