Patent GB-1311772-A (GB)
IPC: H04Q3/00
Filed: 1970-05-28
Abstract: 1311772 Automatic exchange systems COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS CIT-ALCATEL 28 May 1970 [29 May 1969] 25856/70 Heading H4K Line finder/final selectors are provided by crossbar switch bridges each wired to provide n outlets serving subscribers' lines, the n inlets of an array of n such line finder/final selector bridges each being connected by way of a feed bridge to the corresponding n inlets of an array of n crossbar switch bridges, each also wired to provide n outlets, serving as a selector switching stage, corresponding outlets of the selector stag ebridges being multipled and the resulting n multiples being connected to corresponding ones of the line finder/final selector bridge inlets. As shown in Fig. 1, each crossbar switch-bridge has 10 vertical conductors split between groups of horizontal select bars H0 to H3 and H4 to H10. Bridge inlets comprise the wires A, B, C and an identifying wire indicated by a plus sign. The speech wires A and B are connected to the upper portions v 0  and v 1  of the first and second vertical conductors and are selectively connectible to any outlet in any one of four sets of seven bridge outlets in lower vertical conductor portions v<SP>1</SP> 0  to v<SP>1</SP> 7  according to which one of the select bars H 0  to H 3 , and which one of the select bars H 4  to H 10 , are operated. To fully exploit the rectangular contact array of the bridge the C-wire is connected to the lower vertical conductor portion v<SP>1</SP> 8  from which, according to the operated one of select bars H4 to H10, it is connectible to one of the seven sets of four bridge outlets in the upper vertical conductor portions v 2  to v 8 , the particular outlet of each set of four being selected by the operated one of the select bars H0 to H3. The + wire identifies the selected outlet by relaying battery on the effectively unsplit ninth vertical conductor to one of the outlets 0D to 3D and one of D1 to D7, this information being a direct representation of which horizontal select bars are operated. The bridges, such as just described, each constitute a single vertical of a cross-bar switch shown in Fig. 2 where the bridges CC1 and CC2 are multipled to serve as line finder/final selectors for the 28 subscribers A01 to A28 in group G1; bridges CC3 to CC6 serving the 28 subscribers A29 to A56 in group G2; and bridges CC7 to CC10 serving subscribers A57 to A84 in group G3. Each of the bridge inlets has access over a feed circuit AS 1  to AS 10  to a corresponding bridge inlet of a selector cross-bar switch CN1a and also is accessible from a corresponding outlet of the selector switch. Each bridge of the selector switch is wired to provide 28 outlets, as shown in Fig. 1, and corresponding outlets are multipled to provide multiples M1 to M28. To prevent short-circuit connection of a feed circuit the connection of a multiple of CNla to the corresponding inlet is barred in the route selection process of the marker/controller. The selector cross-bar switch CNla has 28 outlet multiples, the full utilization of which according to the invention is seen in the switching group AC of Fig. 3, where three cross-bar switches provide two sets of ten bridges, GC1 to CC10 and CC11 to CC20, and one set of eight bridges CC21 to CC28, each of these bridges being capable of terminating a group of 28 subscribers in the manner shown in Fig. 1 and with the subscribers being multipled over two or more such bridges according to the grade of service required for each group. The 28 bridge inlets of these subscriber switches are connected over feed circuits AS to corresponding bridge inlets of selector cross-bar switches C1, C2, and C3. The 28 outlet multiples of each cross-bar switch C1, C2 and C3 are correspondingly commoned and connected to a corresponding one of the subscriber switch bridge inlets in order to provide call terminations. A further ten bridge cross-bar switch with 28 outlet multiples may be commoned to the multiple of the selector cross-bar switches in order to provide working over bothway external trunks as shown at INT 1 . Connections may be made between two such switching groups, as AC and ACa, by way of a group of feed circuits AS and cross-bar switches with 28 outlet multiples commoned to the respective multiples of the selector cross-bar switches. The bothway external trunk groups of each switching group may be directly connectible to the selector switch outlet multiple of the other switching group by switches shown in dotted outline.