Patent GB-973718-A (GB)
Title: Selection systems for electrical circuits or equipment
IPC: H04Q3/54
Filed: 1962-11-23
Abstract: 973,718. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. Nov. 23, 1962 [Nov. 30, 1961], No. 44412/62. Addition to 946,263. Heading H4K. In the electrical connection system of the parent Specification in which circuits belonging to two different sets are interconnected through a connection network by one particular path, this path having been found by selecting one route from a plurality of marked free routes through a selection network simulating the connection network, the connection network comprises switching devices which require no holding current to maintain them operated and the identity of the switches involved in the connection are stored in a memory device associated with this connection whereby release of the connection may be obtained by passing suitable signals from the memory to the switches. The selecting netwotk and marker are fully described in the parent case and are represented in Fig. 2 by a rectangle MQ. Common control circuits for a junctor (or feed bridge) JTr and a register and the marker have access to the junctors only during certain parts of a time cycle (Fig. 5, not shown) in the manner of a time division system. Setting up a call, Fig. 1. When a calling subscriber is connected to a junctor (or feedbridge) as in the parent Specification, the identity of this junctor JTr, i.e. its position on the banks of synchronous scanners EXJ, EXJ<SP>1</SP>, is recorded in the marker MQ. During the time allocated to the marker for access to the junctors, MQ sends a signal over wire 1 and OR gate 9 which orientates EXJ<SP>1</SP> on to the seized junctor and EXJ on to a magnetic core register (memory) located in JT and associated with the seized junctor. This memory is thereby enabled to receive the identities of all the switches used in the connection, these identities being signalled from MQ over wires 2 using a 3 out of 6 code. At the same time, MQ signals over wire 3 to a free " transfer memory " MT1, the identity of the junctor and of a register located in EN to be associated with this junctor and also the class of service of the calling subscriber, after which MQ releases. When the registers in EN are scanned by EXE during the time allotted to them for access to the junctors, the chosen register is connected to MT1 over wire 5 and thereby it receives the stored information. The next time it is scanned, the register orientates EXJ via wire 6 to the seized junctor and signals over wire 7 to the junctors' control circuit that dial tone should be reverted. Dialled impulses are then recorded in the register as is described in Specification 963,329. The register seizes a free transfer memory MT2 over wire 20 and transmits thereto information regarding the called subscriber which in turn is passed to the marker when the latter becomes available. MQ selects a path between the seized junctor and the called subscriber and then informs the register via MT1 that the connection is completed, whereupon the register causes ringing current to be transmitted from the junctor. Release of connection.-The junctors are scanned under control of DCJ and when a junctor requiring release (dr1 open) is found a signal is passed via EXJ<SP>1</SP>, EXJ to the associated memory circuit located in JT. This information is passed to MT2 over wire 25 and then over wire 22 to MQ during the time interval when the marker can scan the junctors. During the next accession period, MQ orientates EXJ on to the junctor requiring release and receives over wire 23 the identity of the switches involved in the calling side of the connection. These switches are released as described in the parent Specification and the called side of the connection is then similarly restored. Arrangements for subscribers having a special class of service, fig. 4. For a calling subscriber the fact that he requires a special class of service is recorded in the register as mentioned above (although which class he is entitled to, is not yet known) but for all called subscribers the register must first search a store TDS to determine whether a special class of service is required before the connection can be completed. In either case the register seizes a memory MT3 (Figs. 1 and 4), and orientates scanner EXJ on to the particular junctor whose associated memory contains the subscriber's directory number of a " translation " thereof. The translation, the number and the class, of special subscribers are recorded on magnetic cores to1, to2, to3 (Fig. 4) respectively, the cores being arranged in groups 1-10 which correspond to the initial thousands digit of the subscriber's directory numbers. If the directory number is stored in the junctor's memory this is then passed to MT3 and an appropriate scanner EXT1-EXT10 is started. A comparator circuit CP operates when (and if) the numbers in MT3 coincides with one readout from cores to2 whereafter the class of service is signalled over wire 18 to MT3 and thence to the register. Specification 973,717also is referred to.