Patent GB-657612-A (GB)
Title: System for communication of intelligence
IPC: H04Q3/00
Filed: 1945-11-28
Abstract: 657,612. Automatic exchange systems. MODEE, G. V. G., STRANDLUND, J. H., and EK, F. Nov. 28, 1945, No. 32158. [Class 40 (iv)] The stages of a cross-bar system comprise units each consisting of a primary switch, a secondary switch and, in group selectors, a tertiary switch. A set of ten units is controlled by one or more markers. In a group selector a marker comprises a number of cross-bar switches with their own hold magnets and with common select magnets. In a combined line finder and final selector claimed in Specification 657,657, the primary and secondary switches are each subdivided into four sections. A subscriber's line appears in each of the four sections of a primary switch. When the switch is used as a line finder, the marker selects a free trunk from the secondary switch to the next stage and a free link from one of the four calling positions in the primary switch to the secondary switch and operates the switches. When the switch is used as a final selector, it is controlled numerically by marking wires from the third group selector. Markers in successive stages may be connected over paths separate from the trunks, Fig. 42 (not shown). The thousands and hundreds digits of reference numerals indicate the Figure concerned. The system is outlined in Fig. 2. Subscribers lines are connected to a line frame LR. When a subscriber A calls B, he gains access through a line finder SLV1 to an idle first group selector IGV and a register under the control of a marker 313 and register finders 1810, 1812. The number is dialled and the call is extended under the control of the register and of markers 1399, 1499, 3099 in the group selectors IGV, IIGV, IIIGV to the final selector SLV2 and to B. Battery ringing current and tone signals are provided by a feed circuit SNR. The complete system is shown by the figures arranged as shown in Fig. 38. Line finder, Figs. 3, 6-10. A switch with a capacity of 100 lines comprises two primary cross-bars and two secondary cross-bars (Fig. 3a). Each primary cross-bar is divided into two sections (301, 302 : 303, 304), each comprising ten hold magnets. A subscriber's line is multipled to contacts in each section of a primary switch. The corresponding contacts of a pair of sections are arranged side by side (Figs. 3b, 7) to faciliate wiring. The secondary cross-bars are similarly divided into sections and the hold bars are connected alternately to outgoing and incoming trunks. Each primary hold bar is connected to a secondary select bar by a one of forty links. When A (No. XXX00) makes a call to B (No. XXX99) line relay 610 operates and is followed by primary and secondary select magnets 710, 800 corresponding to the tens digit (0-)  and by primary and secondary select magnets 700, 810 for the units digit (- 0). Relays 720, 722 follow the primary select magnets to enable the secondary select magnets to operate and to mark the sections busy. A marker, Fig. 10, determines which of the four contact groups is associated with a free link and searches for a free trunk to the first group selector before operating the hold magnets. Each of the idle-marking relays 1001-1004 corresponds to one of the primary sections 301-304 and is operated over a contact of 720 or 722 and a contact of a hold magnet 350-389 if the section is idle. Relay 1000 follows and relays 1011-1014 corresponding to operated idlemarking relays operate in turn to test the five outgoing trunks 321 of each secondary section by means of relays 1005-1009 and test wires 855. Free trunks are marked by a potential applied in a register 1700. When one or more test relays operate, the search stops, relay 1010 operates and only one test relay is held. The hold magnets of both primary and secondary switches are operated over 1010. The select magnets and the marker are released later when cut-off relay 611 operates. If there is no free trunk, all the idle-marking relays fall back during the tests, relay 1015 operates and the tests are repeated until a trunk falls idle. If all the sections are busy and no idle-marking relays are operated, 1000 does not operate and slow-acting relay 913 operates to disconnect the line relay set by operating relay 620. A slow-acting trouble relay 912 operates if the time taken in a test cycle of the idle-marking relays is excessive. If the finder is tested by a third group selector IIIGV for use as a final selector, ground is connected to conductor 905 by relay 913 and N.U. tone is transmitted. Final selector. When a free final selector is found by a third group selector IIIGV, a call receiving relay 900 and a blocking relay 620 are operated over 901. If the final selector is already operating as a finder and is repeatedly searching the trunks to the first group selector IGV, a call from IIIGV takes precedence and operates relays 620, 900 over a contact of 1015 when that relay is operated at the end of a testing cycle. The wanted tens. and units (- 99) digits are marked over groups of marking wires 907, 908 and the select magnets operate. When an idle-marking relay operates, start relay 1000 follows and marks as free, the test wires 1051-1054 of trunks incoming to the secondary cross-bars. When the third group selector searches and finds a free trunk, it operates the hold magnets 890, 389 over conductor 863 in trunk 3070. Potential on test wire 862 is extended to operate B's cutoff relay and the select magnets in the marker of the third group selector by a signal over conductor 864 when hold magnet 890 operates. In a modification, Figs. 5a, 11, 12 (not shown), the numbers in the primary switches are redistributed. Instead of arranging the contacts of a pair of secondary sections side by side, the sections are separated and are provided with separate sets of select magnets. An auxiliary hold magnet is provided with each pair of secondary sections. First group selector, Figs. 13, 16-23. A unit of this group selector comprises primary, secondary and tertiary switches arranged in ten cross-bars, each with twenty hold magnets. The common marker 1399 comprises an individual cross-bar (Figs. 20, 21), with 20 hold magnets. In the course of extending a connection through the group selector there are three successive select magnet operations in the marker and six successive select magnet operations in one of the ten selector units. After each select magnet operation a hold magnet is operated by ground from a contact of the operated select magnet. The six select magnet operations in the selector are followed respectively by the operation of hold magnets 1812, 1810, 1811, 1901, 1911 and 1821. When a free trunk such as 321 is found by the finder a select magnet 1800, corresponding to the trunk is operated (first select operation) over the call and hold wire 1835. Hold magnet 1812 operates to connect the calling trunk and is followed by relay 1813 which marks the primary switch 1301 busy. Cut-off relay 611 belonging to A operates, releases the common marker of the finder and operates relay 1611 of the register finder. Relays 1814, 1621 follow, the former blocking further calls to the registers from primary switch 1301 and the latter operating any of the test relays 1631- 1640 that are associated with free registers 1700. Relay 1600 is normally operated by a free register. If there is no free register, no connection is extended by the finder. If, subsequent to the operation of 1611, a register that was idle when tested is occupied by another first group selector unit, 1611 is shunted over series contacts of test relays 1631-1640 until a register falls free, when the test is repeated. If one or more of the test relays is energized, 1622 energizes over a contact of the first operated relay in the order 1640-1631, 1623 follows and the select magnet corresponding to the test relay and register is operated (second select operation) over contacts of 1814. Hold magnet 1810 follows to extend the trunk 321 to the free register tested by 1631. The register is then seized over a contact of calling relay 2011 and holds 1812. The register receives the impulses dialled by A, prepares to transmit the code corresponding to the numerical selection to be made in the first group selector and operates the calling relay 2011 of the primary selector, 1301 corresponding to trunk 321. In the common marker, three successive select magnet operations to be mentioned later are followed respectively by the operation of hold magnets 2021, 2123 together, of hold magnet 2124 along with one of the magnets 2111-2120 corresponding to the tertiary switch in which the free outgoing trunk is found and of 2022. Calling relay 2011 operates select magnet 2000 (first marking operation) corresponding to the primary switch 1301 and hold magnets 2021, 2123 follow. The former hold magnet connects the control wires from the register to code relays 2201-2204 over the contact bars 2-4, operates 2200 and also marks circuits over which a select magnet in the switch 1301 can be operated with hold magnet 1811 to connect one of the links 1331-1340 to the trunk 321. The latter hold magnet connects to test relays 2101-2110 the test wires of the links 1331-1340 outgoing from 1301. Relay 2205 follows relay 2200 and interrupts the circuits of 2200 to release the marker if relay 2206 is not operated by a numerical signal from the register before slow-acting relay 2200 can release. At least one of the relays 2201- 2204 is operated by each code signal. The test wires of the links 1331-1340 are grounded when busy and operate 2101-2110 to indicate the inaccessible secondary switches of the series 1311-1320. Each hold magnet 2111- 2120 corresponds to a tertiary switch 1321- 1330 already marked accessible or inaccessible by marking of the corresponding secondary switches 1311-1320. The five bars of each magnet correspond to the five hold bars or trunks in each row of the tertiary switch. If the selected numerical group is the ninth, select magnet 2009 is