Fuente: Wipo "digitalization" 731,779. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Sept. 25, 1953 [Jan. 6, 1953], No. 26448/53. Class 40 (4). A cross-bar system comprises a blocktranslator with means for translating the directory number into information indicating the location of a line and the number of the station on a party-line, said information being transmitted by the block-translator to a blockcoupler between the thousands-link frame and the block-link frame. The cross-bar switches may be of the type described in Specification 576,834 with ten horizontal connections and a varying number of vertical connections. The line-link frames each serve 250 lines divided into groups of 25 with a 10 x 10 spread between primary and secondary switches as shown in Fig. 3, part 1. A similar spread is used on the thousands-link and block-link frames, these links being arranged in pairs, each comprising an upper and a lower link. Between each thousands trunk and its assigned vertical on the block-link primary switch is a block coupler comprising a number of control relays and a hundreds, tens, and units register to select the called line in the switching block concerned. It also comprises a thousands register to control the supply of ringing current to the various parties on a party line. The Specification first describes the operation of the system schematically with reference to Fig. 2 (not shown), then in more detail with reference to Fig. 3 (only part 1 shown). The Specification goes on to describe the operation, still somewhat schematically, with reference to Figs. 4-9 and finally in complete detail with reference to the remaining Figures. Semi - schematic description, Figs. 4-9. Initiation of call. When the subscriber at station S1 closes his loop, line relay 401 pulls up to ground conductor M individual to the calling line and conductor F common to the fives group comprising the calling line. Ground on conductor F is applied through fives resistor FR1 to primary conductor P common to the 25 lines served by primary switch 800A1 to cause line controller 1200A1 to operate line controller switches 1000A1 and 1100A1 with reference to the group of five lines including the calling line. Line controller 1200A1 then matches an idle path from the calling line to an originating trunk 1-203A1 over line-link 202A, the test for an idle or busy line-link being made over resistor LR and link-test conductor LT. Line controller 1200A1 then grounds link-select magnet wire LSM to operate the primary and secondary select magnets SM404 and 5M405 associated with line link 202A, whereupon a circuit over wire PS-ON causes the controller to operate the hold magnets HM403 and HM406 to extend the calling line to the matched originating trunk 1-203A1. HM403 operates in series with lock-out relay 402 and restores line relay 401. HM406 locks to ground on the sleeve conductor of the seized originating trunk. Seizure of thousands coupler, Fig. 5, and thousands controller, Fig. 6. When the local thousands coupler 1000 is seized line relay 1002 operates to energize release relay 1004 which returns ground over the sleeve conductor S to dismiss the line controller 1200A1 and switches 1000A1, 1100A1. As described later, coupler 1000 returns dial tone to the calling line. Line relay 1002 repeats the dialled digits over wire 1028 to the digit registers (not shown in Fig. 5). According to the first digit the initial digit register makes connection with one of the digit leads in cable 1-281 extending to the digit relays 1500, Fig. 6. For an outgoing call the thousands controller 1400 is called in to extend the connection across the thousands link frame to the desired outgoing trunk. For a local call no switching takes place at 1500 because the corresponding initial digit lead is left open and the thousands controller is called in only after the receipt of the thousands digit. Terminating call. Seizure of thousands trunk. Local calls handled by local thousands coupler 1000 and incomi