Patent GB-103842-A (GB)
Title: Improvements in and relating to Means and Apparatus for Controlling Alternating Currents such as are used in Wireless Signalling Systems.
IPC: H04L27/04
Filed: 1916-02-04
Abstract: 103,842. British Thomson-Houston Co., (General Electric Co.). Feb. 4, 1916. Telephonic, telegraphic, and other non-contactmaking relays.-In a system for the control of highfrequency alternating currents, such as are used for wireless signalling transmission, as described in Specification 7151/13, the signalling or controlling windings of the magnetic controller are arranged to cover substantially the whole of the magnetic circuit of the high-frequency windings, which are so arranged that their inductive effect on the controlling-windings is neutralised. The high-frequency windings are connected in series or in parallel, and in the latter case, condensers are arranged in series with each winding and in shunt to both. Figs. 1 and 2 show two forms of the controller, in which the high-frequency windings 2 are wound separately on two parallel bars 1, which both lie within the controlling-winding 4. The flux due to the windings 2 is local to the magnetic circuit 1, 3, whereas the flux due to the controlling-winding 4 forms two parallel circuits 1, 5 in the form shown in Fig. 1, and flows completely round the large rectangular circuit in the form shown in Fig. 2. In another form, the highfrequency coils are wound round two annular cores placed opposite and parallel to each other, and the controlling-winding completely encloses both rings and the space between them. A construction of a controller of the shape shown in Fig. 1 is shown in cross-section in Fig. 5. The core is built up of composite plates each formed of extremely thin layers of magnetic material, for example electrolytic iron, silicon steel, or iron scale obtained in the annealing of silicon steel, alternating with layers of insulating-material, such as paper, the permeability thus being substantially independent of the frequency. The parallel composite plates 19, 23, 24, 25, about one-sixteenth of an inch thick and separated by spaces for cooling by air or liquid, are held together and to a frame 27, 28 by bolts 29. The composite plates 19 forming the magnetic circuit of the high-frequency windings 20 are in the form of hollow rectangles separated at each shorter end by plates 22, which are interleaved with the plates 23 forming the vertical part of the magnetic circuit of the controlling-windings 26. The laminations of the plates 23, 24, 25, which do not carry the high-frequency flux, need not be as thin as those of the plates 19. When annular cores are used, they may be formed by winding continuous thin strips of magnetic metal and insulating-material to form cylindrical elements of different diameters, which are then built up concentrically with spaces between adjacent elements for cooling. The cross-section of the high-frequency magnetic circuit may vary at different points. In the circuit connexions shown in Fig. 6, the series high-frequency windings 33 are placed in shunt to the aerial 30 across the secondary of a transformer 32, the primary of which is connected to a high-frequency generator 31. One controlling-winding 34 is in circuit with a battery 35 and signalling-key 36, and the other 37 is energized by a battery 38, the two batteries assisting each other. Rectified current, obtained through a valve 40 from a coil 39 coupled to a coil connected across the windings 33, is also led to the winding 37 and opposes the battery current. An inductance 44 shields the battery 38 from the rectified intermittent current. Rheostats 41, 42 are adjusted so that, when the voltage across the windings 33 is at a maximum, the current derived from the coupling 39 balances that due to the battery 38, and the control winding 37 is de-energized. When the key 36 is opened, the impedance of the coil 33 is increased and the voltage across it increases, so that more rectified current opposes the battery current in the coil 37, and the core magnetization is further diminished and its impedance increased. Signalling thus mav be effected with a small energizing - current for the winding 34. The inductance of this circuit is kept low in comparison with its resistance. In a modification, Fig. 7, the same coils 48, 49 are used for the high-frequency and the controlling currents. The generator 46 is in the antenna circuit, and the two high-frequency windings are in shunt to the generator, condensers 52, 53 being included in each shunt. The control circuit contains the battery 51, key 50. and the two windings 48, 49 in series, the condensers 52 presenting the short-circuiting of the battery. In the arrangement shown in Fig. 12, the two branches of the highfrequency windings 33 are in parallel, and each branch includes a condenser 58, 59, while a third condenser 60 shunts both branches. The condensers 58, 59 are of such capacity that the shunt containing the condenser 60 forms a short circuit for currents of radio-frequency, and an open circuit for telephone currents. The control circuit 34 includes a rectifying-valve 71 and is inductively coupled to a circuit containing a second controller 69 and a winding 68 on the alternator. The control winding 72 of the controller 69 is energized by a battery, and the current is varied by a microphone. In another arrangement the microphone circuit acts inductively on the circuit of the winding 34, the second controller 69 being omitted.