Patent GB-1181183-A (GB)
Title: Automatic Telecommunication Exchange
IPC: H04Q3/00
Filed: 1968-01-11
Abstract: 1,181,183. Automatic exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 11 Jan., 1968 [23 Jan., 1967], No. 1734/68. Heading H4K. A telephone exchange has a plurality of switching networks each of n switching stages, n marking circuits each serving all the correspondingly located stages in the switching networks. As shown in Fig. 1, connections between junctors JUC and line circuits are set up over stages ST1 to ST4 of one network while connections between the junctors JUC and outgoing trunk circuits OTC are set up over stages ST5 to ST8 of a second network. The marking arrangement comprises a section TM selecting and controlling junctors JUC and comprises the sections TM1 to TM4 controlling the corresponding pairs of stages ST1 and ST5, ST2 and ST6, ST3 and ST7, ST4 and ST8. With 128 junctors JUC a seven-bit code directs marker section TM to select a junctor and operates contacts r, t, s. A further bit operates switch T1 or T2 to select the line or trunk side of the junctor. Switches T1 and T2 and a switch T are common to all junctors and are preferably transistors operated after mechanical contacts r, t, 8 have been made. When setting up a connection from the line side of a junctor, switches T and T1 are operated to apply positive battery to the line side terminal I of the junctor and to operate relay Hr which connects earth to the terminal I held off by diode d<SP>1</SP>11. The relay matrix of each stage is controlled by four marking wires over which diodes, such as d<SP>1</SP>1 find earth by way of selectively actuated marking contacts such as It and a common transistor current switch such as T3. Operation of a matrix relay such as Lar extends the positive battery from the junctor into the next stage where a further matrix relay will operate when marking earth is removed from the preceding stage. When connection is extended over stage ST4 a line relay Cor operates and provides positive battery to hold the connection to earth over diode d<SP>1</SP>11 in the junctor. The marking circuits may now retire the marking earths presented to the junctor-to-outgoing- trunk network having been without effect as no battery was presented to this network from the junctor. If each marking section TM1 to TM4 has four marking leads g1 to g4 common to the corresponding stages of each network, selection of one such marking lead is effected in the 2 x 2 relay matrix of Fig. 3. The relays Ltr1 to Ltr4 of this matrix are selected by column wires x, y, and row wires u, v, governed respectively by bi-stable circuits BS1, BS2. A bi-stable BS3 prepares the matrix. An alternative arrangement is shown in Fig. 4 for a system in which a marking section such as TM1 controls a switching stage in each of two networks, a separate set of 16 marking leads extending from the marking section to each switching stage. The 32 marking leads are selected in the marking section by operating one of 4 x 8 matrix of relays Ltr. Co-ordinate selection of a relay Ltr to mark the corresponding lead g is effected by two bi-stables BS4 and BS5 to operate a selected one of four relays Rir to Rlr to select a matrix row, and by three bi-stables BS1 to BS3 controlling eight relays Rar to Rhr to select a column. Row and column selecting contacts each connect a resistor into a chain circuit as well as connecting a row or a column. If more than one row or column is selected an alarm circuit PD1 or PD2 is activated. Each row wire is monitored, over a resistor such as Rli or R1l, by an alarm circuit PD3 which detects abnormal current flow if one of the matrix diodes d1 to d32 should fail. The matrix of relays Ltr may be controlled by a second set of bi-stables BS1 to BS5 with a second set of row and column selecting relays Rar to Rlr with a second associated resistive chain checking circuit. Each marking section may by this means be set up with the identities of two marking leads at the same time, the matrices of relays Ltr being used to select the marking leads for a connection in one network using one of the identities registered before being used to select the marking leads for a connection in the other network using the second identities registered.