GB323244A - Improvements in systems for reducing the disturbances caused by apparatus capable of producing high frequency interference with radio receiving apparatus - Google Patents

Abstract

323,244. Gerhardt, O. July 18, 1928. Protective arrangements.-Apparatus capable of generating high frequency disturbances to which radio receiving apparatus may be sensitive is provided with a capacity in shunt to the source of such disturbances and a choking coil or coils in the supply leads to prevent transmission to external conductors. The capacity may be a condenser or may take the form of a metallic shield or casing permanently earthed or earthed through the body of the user. A motor M may have a condenser D across its terminals and inductances 8 in the supply leads. A dynamo-electric machine, Fig. 2, may be provided with auxiliary brushes c, d to each of which are connected condenser electrodes D', D<2> arranged between electrodes D<3>, D<4> connected to the main terminals. A trolly collector, Fig. 3, may have one or two auxiliary collectors H<1>, H' in parallel with the main collectors R with a condenser D<1>, D<3> in series. An inductance 8 may be placed in the lead supplying the lighting circuit derived from the trolly. Therapeutic radiation and high frequency apparatus, Fig. 5, comprising a primary oscillating coil 1, interrupter 2 and Tesla transformer 4, 5 supplying a vacuum tube 6 may have choking coils 8 in the leading-in wires and a metallic casing G enclosing all but the radiating aperture H and permanently earthed or adapted to be earthed by contact with the hand of the operator or with the patient. The casing may be in separate portions, enclosing the tube, Tesla coil and primary oscillator respectively and connected together by sections of knitted metal-fabric sheathing enclosing the connecting wires or by a simple metallic connection. The condensers in series, D<2>, D<3>, Fig. 6, may be shunted between the leading-in wires with their common terminal connected to the casing, or one end of the Tesla coil secondary and the earthed casing may be connected to separate intermediate electrodes of a condenser D<2>, D<3> as shown in Fig. 8. Condensers for this purpose may be constructed as indicated in Fig. 7. The circuits of the Tesla coil may be connected as shown in Fig. 9, condensers D<2>, D<3> being in series with the leads from the primary oscillator and the coil windings being connected to the casing. The primary oscillating coil 1 may supersede one of the choking coils 8 in this arrangement. A vacuum tube lighting arrangement with similar supply circuits is shown in Fig. 11, the apparatus being enclosed in a metal casing having an opening for the tube with a metal shield 7 which may form a reflector behind. A system suitable for advertising has an external tube enclosed in a sheath of wire grating or netting connected with the casing.