Patent GB-901837-A (GB)
Title: Improvements relating to selectrive electrical marking arrangements
Inventor: KINSEY RONALD WILLIAM STANLEY
IPC: H04M3/523
Filed: 1960-02-25
Abstract: 901,837. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Feb. 8, 1961 [Feb. 25, 1960], No. 6701/60. Class 40 (4). In an arrangement for the individual selection and marking of a plurality of co-ordinatelygrouped lines by means of a marker functioning on a group basis, there is provided for each line, L1, for coding its identity for selection by the marker and for decoding its selection when made by the marker, a bi-functional gate, G1, comprising an input/output path, jl, including switching means, VTL1, operable to establish current flow through this path, and a number of encoding and decoding branch paths which lead to the marker and of which one branch path includes a transistor, GT1, which, with said switching means operated, passes encoding current of characteristic amplitude or direction through that branch path but is switchable from the marker to pass decoding current differing in respect of such characteristic from the encoding current, the input/output path of the gate having associated therewith discriminating means, RB1, operable in response only to decoding current flow in the transistor, GT1, for marking the appertaining line, L1, as having been selected. In order that both calling and called lines may be marked, the decoding part of the arrangement including the bi-functional gate, operates on a directory number basis, the directory number terminal DT1 being jumpered to the equipment position number terminal ETm to which the line circuit including relay RB1 is connected. Operation in response to a calling line.-The switching transistors such as VTL 1 are normally non-conductive so that - 12 v. is applied to the input/output paths j1 . . . j100 of the gates G1 . . . G100. When the line L1 is looped, the resulting - 5 v. on the base of VTL1 causes it to conduct and its emitter potential of - 4 v. is applied over j1. The gate diode GD1 is thus forward biased and changes the potential on the X-ordinate lead XI from its quiescent value of - 10 v. (via RX1) to a calling potential of - 5 v. The condition of the switches cc1, cc2 (which are preferably electronic switches) determines whether the gate matrix may be used for marking called or calling lines. In the condition shown, a called line may be marked and it is assumed that these switches are recurrently operated and released to permit calling and called line marking alternately. The X-ordinate leads X1 ... X10 are connected via rectifiers DX1 ... DX10 to one side of the D.C. control windings of respective saturable reactors SRX1 . . . SRX10, the other sides of which windings are commoned to earth via resistor RM and rectifier DM in parallel. With cc1 unoperated the diodes DX1 ... DX10 are reverse biased and no further action takes place until cc1 closes. Then the - 8 v. potential connected up reverse biases DM and forward biases those of DX1 . . . DX10 connected to X-ordinate leads having the - 5 v. calling potential, whereupon current flows in the control windings of the corresponding saturable reactors of SRX1 ... SRX10. The outputs from the A.C. windings of the relevant saturable reactors are fed to voltage doubling and rectifying net works NX1 ... NX10 so that the potentials of the relevant cathodes of the multi-cathode tube DKX are reduced to about +90 v., whereupon an anode-cathode discharge takes place to one of these cathodes, thus selecting one of the calling groups. The discharge current flows in the D.C. winding of the relevant one of SRA1 ... SRA10, say SRA1, and the A.C. output is fed to a voltage doubling and rectifying network NA1. As a result, the base of the NPN transistor AT1 is raised from- 12 v. to - 2 v., AT1 conducts, and its emitter potential of - 8 v. is applied to the X<SP>1</SP>1 marking lead. All the gate transistors, such as GT1, having their bases connected to lead X<SP>1</SP>1, and the - 5 v. calling potential connected to their electrodes ec2 then conduct current in the direction ec2 to ec1. With GT1 thus conducting the potential of the Y-ordinate lead Y1 changes from its normal - 10 v. (via RY1) to the - 5 v. calling potential. If any other lines in group X1 are calling, similar changes occur on the relevant ones of leads Y2 ... Y10. The tube DKY selects one of these Y-ordinate leads, say Y1, and as a result the base potential of PNP transistor BT1 falls from its normal + 6 v. to - 4 v., BT1 conducts, and the potential of Y1 approximates to earth potential. GT1 now has its base at - 8 v., and ec2 at - 5 v., so the earth on ecl causes reversal of the emitter-collector current, whereupon the potential at j1 becomes earth potential. The line circuit rectifier is thus reverse biased and RB1 operates, in series with MD1, to mark the calling line which has been selected. After connection has been made to this line by crosspoint switching means (not shown) under control of RB1, a positive voltage, clamped to about +¢v. by CD1, is applied to the base of VTL1 to cut it off and remove the - 5 v. calling potential. RB1 remains held until GT1 ceases conduction on the release of switches cc1 and cc2. Marking a called line.-The terminals MX1 ... MX10 and MY1 ... MY10 are normally at - 10 v. and it is arranged that when a called line is to be marked the MX and MY terminals corresponding to its two digits have their potential raised to + 6 v. The relevant DXM and DYM rectifiers are thus forward biased and current flows through the control windings of the corresponding SRX and SRY saturable reactors, the called line then being marked in the same manner as was the calling line. Modifications.-If desired the symmetrical transistors may be replaced by asymmetrical ones with their collectors connected to the input/ output paths. By including a transistor in each X-ordinate lead such as X1 it is possible to replace the decoupling diodes such as GD1 by decoupling resistors (Fig. 3, not shown), a separate control winding being provided on each SRX saturable reactor which is switched in by cc1 for called line marking.