GB471193A - Improvements in electric signalling systems - Google Patents

Abstract

471,193. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. Feb. 29, 1936, No. 6195. Convention date, March 2, 1935. [Class 40 (iv)] [Also in Group XL] Discharge-tube apparatus with a controllable ray, for example, a cathode-ray tube, is used as selecting and connecting apparatus in an electric signalling system, for example, as a finder or selector in an automatic telephone exchange. In the cathode-ray tube, Fig. 1, connection between a sender S and one of a plurality of receivers M1 ... M4 is effected by applying suitable potentials to plates SP thereby causing the ray to strike a corresponding terminal member at the end of the tube. Two tubes acting respectively as a finder and connector may be arranged with their cathodes connected together and in a modification two rays acting respectively as finder and connector may be provided in a single tube with a single field of contacts. In a two-wire connection, a tube must be included in each wire and a section containing such tubes may be connected to the lines at each end through transformers having their mid-points connected together. In the tube, Fig. 5, comprising evacuated and gas-filled chambers separated by a screen V, the cathode-ray acts temporarily through one of a series of windows F to cause a dischargeconnection to be established between perforated plates or grids SN1, SN2 connected to the two conductors of a link-circuit and contacts E1, E2 connected to a subscriber's line. The grids and contacts may be replaced by horizontal and vertical strips, respectively, by which connections may be established or required between six subscribers' lines and six linkcircuits. In the tube K, Fig. 8, the cathoderay controls pairs of grids in a hot-cathode gas-filled discharge tube TY whereby dischargeconnections are established through the tube TY between any two subgcribers A1 ... A4. Control of the potential on plates SP by received impulses is effected by charging a condenser C1 over contact 1 at the beginning of each digit and transferring a portion of its charge to a smaller condenser G2 at each operation of impulse contacts 2. The stream of secondary electrons produced by the striking of a cathode-ray against one of the terminal members at the end of the tube may be employed as the connecting circuit. The cathoderay tube may be provided with a control grid and such a tube with one line connected to the grid and cathode and the other to the anode and cathode acts as a one-way amplifier. The Specification as open to inspection under Sect. 91 comprises also constructions of discharge-tube selectors forming the subjectmatter of Specification 471,194. This does not appear in the Specification as accepted.