Patent GB-683911-A (GB)
Title: Improvements in station identification circuits for telephone systems
IPC: H04M15/08
Filed: 1950-04-21
Abstract: 683,911. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. April 21, 1950 [April 26, 1949], No. 9863/50. Class 40 (iv). In a substation identification circuit which comprises an electronic device for each substation, the electronic device corresponding to the substation to be identified is first partially operated, usually together with similar devices corresponding to other substations, and is then wholly operated alone to indicate the particular substation concerned. As shown, substations A, B, C, D on a four-party line L correspond to electronic devices Va, Vb, Vc, Vd respectively, each in the form of a gas-filled tube having a single cathode and a plurality of similar anodes. One anode of each tube is connected to the sleeve conductor S of the line L while the remaining anodes are selectively cross-connected to the relevant members of groups of bus-bars corresponding to " party," " office," " thousands," " hundreds," " tens," " units and " class of service." Each bus-bar except those in the " party " group is connected to a detecting tube such as V20, Fig. 3, which is further connected to a pair of screen grid thyratron register tubes such as V30 and V30<SP>1</SP> controlling the magnets PM of a recording device RD which may be of the type described in Specification 657,553, [Group XIX]. Operation of circuit. When a substation, say B, initiates a call and the connection is extended to a trunk TR, a known identification circuit SI, Fig. 2, operates a register relay B, thereby connecting conductor PTY to the " party " bus-bar corresponding to party B. Subsequently a control relay is energized to start the operation of a control circuit, Fig. 6, which applies pulses of various amplitudes and durations, Fig. 7, to conductors SL1, PTY, PX and Rd. Conductor SL1 is connected to conductor S so that the " sleeve " pulse fires tubes Va, Vb, Vc, Vd. When the " sleeve " pulse ends, the " party " pulse, which is insufficient to fire a tube but sufficient to maintain the ionization of a tube already fired, persists on conductor PTY which is extended over a " party " bus-bar to tube Vb. Hence, tubes Va, Vc, Vd are extinguished while tube Vb remains activated. A " read " pulse of the same amplitude as the " party " pulse is now applied by the control circuit to conductor Rd which is connected to all the detecting tubes V20 and their associated bus-bars. In each group of bus-bars the one connected to an anode of the tube Vb becomes conducting while the others do not, so that all the detecting tubes V20 receive sufficient voltage to fire them except those connected over conducting busbars to tube Vb. The positive potential maintained on the anode of each unfired tube V20 primes its associated register tubes V30, V301. If one and only one tube V20 remains unfired in each group, a checking circuit, Figs. 4, 5, applies a positive pulse to a conductor OK connected to the screen grids of all the register tubes V30, V301. The primed register tubes associated with the non-conducting tubes V20 thereupon operate and cause the recording device RD to record the calling substation's directory number and other required information in a predetermined code. If, however, none or more than one tube V20 remains unoperated in one or more groups, the checking circuit applies a pulse to a conductor NG connected to the control circuit which initiates a further attempt at identification. The number of such attempts may be limited by suitable control means (not shown). In the case of a P.B.X., Fig. 1A, the sleeve conductors connected to the firing anodes of the individual substation tubes are also connected to respective anodes of a collector tube COL. The cathode of tube COL is connected to the control anode of a vacuum tube AMP of which the main anode is connected to conductor PX and the cathode is connected to the " party " anode of that substation tube of the P.B.X. group to which the directory number for the group is assigned. No " party " busbars are connected, and the function of the " party pulse on conductor PTY is taken over by the " P.B.X." pulse on conductor PX.