Patent GB-707735-A (GB)
Title: System for the scanning and selection of electrical circuits or equipments
IPC: H04Q1/18
Filed: 1950-05-05
Abstract: 707,735. Automatic exchange equipment. STANDARD TELEPHONES & CABLES, Ltd. May 5, 1950 [May 24, 1949], No. 11160/50. Class 40 (4) In a selective signalling receiver means is provided which responds to the coincidence of a pulse of electrical energy in any one of a number of time positions in a first recurring cycle of time positions with a pulse in any one of a number of time positions in a second receiving cycle of time positions. As described the receiver is used to control group or final selection in an automatic telephone exchange in which the switches in the talking circuit are preferably cross-bar switches, and each free outlet reverts a pulse on its test wire. Principle of operation, Fig. 1.-The terminals B of the cold cathode tubes V are connected to sources of impulses Q1 to Q4 respectively (Fig. 2), and the points Jc are multipled via individual rectifiers Rc to wire W on which a signal is received over the switch wiper sx. The battery Bt1 is assumed to be of 150 volts, the potential sources to produce - 100 volts normally and - 50 volts during impulses, and a tube to be ionized when the cathode/control electrode potential difference is 100 volts. Hence - 50V is an effective potential on the control electrode, but - 100V is not. Contact cx is closed and it is assumed that sx is placed on contact C2 (Q2). When Ql sends an impulse on B1, the point Jc 1 is at a higher potential than contact C2 and the resulting current flow and potential drop in Rh1 reduces the potential at Jc1 to - 100V, so that Va cannot fire. The -100V potential is simultaneously applied to B2, B3, B4 so that tubes Vb, Vc, Vd cannot fire. When Q2 sends an impulse tubes Va, Vc, Vd cannot fire since B1, B3, B4 are at - 100V, but B2 and C2 simultaneously receive a - 50V impulse so that Jc2 and W are at the same potential and Vb fires. Tube Vb remains fired and relay Rb held after the impulse ends. The resulting drop of potential in resistance R raises the cathode potentials of Va, Vc and Vd so that they are no longer capable of operating to a control electrode potential of - 50V. This arrangement permits the selection of a free line from a group searched by sx, the presence of the Q impulses on the C terminals denoting free lines and the relevant relay Ra, . . . Rd selecting the first free one. Receiver responding to signal in a particular group, Fig. 3.-The lines comprising the outlets of a selector are arranged in groups, it being assumed that there are three groups of three lines corresponding to the tubes Val, Va2, Va3; Vb1, Vb2, Vb3; and Vcl, Vc2, Vc3: each being associated with a relay, e.g. Ra1, which may control the vertical magnet of an outgoing line in a cross-bar switch. The control electrodes of the 1, 2, and 3 tubes are multipled to terminals B1, B2, B3 which are connected to sources Q1, Q2, Q3 respectively, and the control electrodes of the tubes of each group a, b, c, are multipled to terminals B<SP>1</SP>1, B<SP>1</SP>2, B<SP>1</SP>3, which are connected to sources PI, P2, P3, respectively. As shown in Fig. 2, the length of each P impulse is at least equal to one complete cycle of Q impulses. The impulses received on the terminals B are effective only if an impulse is received on the relevant B<SP>1</SP> terminal at the same time. The control electrodes are also connected via individual rectifiers to a signalling wire W1 which may be extended by switch sx1 to one of contacts C<SP>1</SP>1 to C<SP>1</SP>3 connected to the sources Pl, P2, P3. The xa, xb, and xc contacts are closed when the lines are idle. Operation assuming signalling wire W2 and its associated circuits do not exist.-The connection of sx1 to one of the C<SP>1</SP> terminals, say C<SP>1</SP>2, ensures that only those tubes in the second group (i.e. connected to B<SP>1</SP>2) may be fired. Hence, during the transmission of the P2 impulse, the tubes Vb 1, Vb2, Vb3 are enabled in turn and the tube corresponding to the first idle line in the group fires. This arrangement may control a group selector or PBX final selector. Operation with W2.-Wire W2 is connected via'individual rectifiers to the control electrodes of the tubes and may be extended by sx 2 to C1, C2, or C3 connected to Q1, Q2 and Q3 respectively. Then the signal on wire W2 effects the firing of a particular tube in the group marked over sx1 and the arrangement may control a final selector. Modification with one signalling wire: Fig. 4 (not shown).-The switches sx1, sx2 of Fig. 3 are multipled to the single signalling wire W via individual rectifiers, and a battery providing - 50V is connected via a resistance to the multipling point. The - 50V potential then appears on W only if the Q and P sources connected up by sx1 and sx2 simultaneously send an impulse.