Patent GB-1127384-A (GB)
Title: Automatic telecommunications exchange
IPC: H04Q3/54
Filed: 1966-01-28
Abstract: 1,127,384. Automatic exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 28 Jan., 1966 [3 Feb., 1965], No. 3899/66. Heading H4K. Four cross-bar switches (each comprising two ganged switches to give a total of sixteen bridge magnets per switch and shown as A, B, C, D in Figs. 13-16) have corresponding splits in their bridge commons to define an upper multiple field across all the switches for local lines and register appearances; a middle multiple field over which registers, feed bridges, incoming and outgoing trunks, and interswitch trunks called web circuits are distributed; and a bottom multiple field over which interswitch trunks called junctors as well as web circuits are distributed. The switches are wired for triple group working (three bridge commons per bridge). Auxiliary select magnets in each split bridge section control the bridging of splits from any one of the bridge commons in one section to any one of the bridge commons in either of the other two split sections. Local lines appear in groups of six such as L0 to L5 shown in Fig. 12, where, in either of two bridges V0, V1, the lines L0 to L2 are available to the bridge commons when the select magnet 323 operates one way; operation the other way making L3 to L5 available. The wanted particular line of the set of three so connected is selected by the appropriate auxiliary select magnet which gives the line access to the bridge outlet. Such groups of lines are illustrated in Figs. 13-16 as boxes 00 to 37, each group having four appearances distributed over the switches A, B, C, D. As each line appears twice in its group this gives eight appearances for each line over all the switches. Trunk circuits T, register-senders R/S, web circuits K, and junctor circuits J, are distributed over the switches in similar manner and as shown in Figs. 13-16. Connections between trunks and lines are preferably set up direct over a single bridge but there is coincidence between a given line and a given trunk on only one bridge. If that path is busy there are seven other line appearances each having access to two junctors in the bottom split multiples, each junctor having access to one of seven trunks. Such a second choice connection extends from the upper multiple field to the bottom field, across the bottom field to another switch from which a bridge connection takes it to the trunk in the middle field. If none of these paths is available each line has access to four web circuit appearances in the middle multiple field, such web circuits taking a path to appearances in the bottom multiple field from which a connection may be set up by bridging a split bridge multiple to reach the trunk in the middle multiple field. Local call.-A calling condition is signalled to a marker which responds by connecting a register-sender to the calling line. If the first three digits indicate a local call the marker releases to be reseized when all seven are received. A translator is called in to obtain the equipment number of the wanted line in accordance with which the marker connects the calling and called terminals to each side of a feed bridge in the middle multiple field. Ringing is connected over the junctor; an appropriate ringing current being selected by setting a switch (Fig. 6, not shown). Trunk call.-In response to the dialled trunk call code the marker records the identity of the register-sender and seizes an idle trunk which it connects to the sender and retires. The sender repeats the required digits to the distant exchange and having done so reenlists the marker to make a direct connection between calling line and trunk. The marker tests for continuity before retiring from any established connection.