Patent GB-658784-A (GB)
Title: Switching system for establishing a plurality of connections by means of one or more switches comprising coordinate magnets
IPC: H04Q3/00
Filed: 1948-11-12
Abstract: 658,784. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Nov. 12, 1948, No. 29449. Convention date, Nov. 18, 1947. [Class 40 (iv)] A system of co-ordinate switches is able, for a number of simultaneous connections at one switching stage, to perform selecting and/or hunting operations under the control of separate register controllers, one of which is operative for each of the connections to be built up. To increase the traffic handling capacity of each outlet of a switching stage the number of connecting-links may be doubled. Connecting links. In Fig. 2, 600 1st group selectors give access to 10 numerical groups of 60 2nd group selectors via twice the number of connections, the connections being arranged homogeneously so that the different splits may help one another out in handling the traffic, and hunting for a free outlet may start from any point in the arc so that a home position is not required. In Fig. 5, 50 inlets have access through primary and secondary cross-bar switches to 100 outlets by splitting the secondary switches vertically, whereby 5 verticals have access to 10 horizontals each. In Fig. 6, each inlet is connected to both halves of a 10 Î 20 cross-bar switch so as to have access to two groups of 10 links, each group having access to all the secondary switches. Figs. 7, 7A show a primary switch P and a secondary switch S, each cross-point having 6 contacts a-f. Common to all inlets is a selector comprising a rotary switch PF with 9 brushes I-IV, V1-V5 wiping over 100 sets of terminals, each set being associated with one of the outlets. Free test potential characteristic of the numerical groups served by the switching stage is offered to the preceding stage from a source of A.C. potential # 1-10 over a contact of break jack BJ to lead f1, and if a hunting selector of the preceding stage, controlled by a register, stops on this potential, the register tests on lead e1 for the presence of battery indicating an idle switch, which operates test relays in the preceding selector. The register now energizes relay Ar over lead d1, to cut out the A.C. and D.C. test potentials at contacts A3, A4, and earth leads a1, e1 to signal the register that a local switching stage is engaged, requiring the register to continue its operations with multi-potential markings. For distant or local junctions not requiring further selections, the signal is sent by disconnecting battery from only one of the leads a1, e1. Relay Ar starts the selector switch hunting by operating magnet PF, and connects leads b1, c1 to brushes IV, III so that the switch explores the potentials on outlet leads f2, e2. A.C. potential on lead f2 is thus transmitted to the register, a phase discriminator of the type described in Specification 565,785 operating when a free outlet of the desired type is encountered, to energize relay Tr and an anode relay in the register. Tr releases magnet PF to stop the selector and energizes relays Br, Cr, the former operating the horizontal magnet HS of the associated secondary switch, which applies ground over brush I of the selector via a strap interconnecting the terminals associated with the group of 10 outlets connected in one secondary switch to those primary magnets HP corresponding to the links serving this group. The anode relay causes the register to check for D.C. potential in the selected outlet, a free outlet operating test relays over lead c1, brush III and lead e2, a double test preventing more than one split seizing the outlet. The register then disables the phase discriminator to release the anode relay and relay Tr, which releases Cr while Br begins to release slowly. Cr operates Dr, Er in series.  The register now repeats the test over lead b1 for the presence of correct A.C. potential, a correct test re-operating the phase discriminator to re-energize the anode relay and Tr, which maintains Br and re-operates Cr to energize Fr, which grounds lead f2. The anode relay removes ground from.lead d1 to cause magnet VP to energize, closing the cross-point Pa-f, whereby the inlet is connected to a link extending to a vertical member of the selected secondary switch and a ground on contact Pf operates the vertical magnet VS to close the cross-point Sa-f, to connect with the outlet engaged by the selector PF. Magnet VP also dismisses the common selector circuit and restores Tr to release Br, Cr, the former restoring Dr, Er, Fr and HS, which releases the magnets HP of all related primary switches so that all horizontal members are restored except those held by the operated condition of a vertical magnet. Release of Fr permits the selector switch PF to hunt for other calls. The connection is broken down when ground is removed from lead f to restore Ar and VP, opening cross-points Pa-f and releasing VS which opens Sa-f, which disconnects ground from lead f2 to release the next switching stage. Simultaneous calls. If two or more inlets in a split are engaged simultaneously for a call and the registers require outlets in different numerical groups, the register which first finds the required potential on lead f2 establishes its connection, the others waiting until the common selector is freed. If the registers require outlets in the same group, when the desired A.C. potential is encountered, the phase discriminators at all registers concerned operate simultaneously and all these registers start the D.C. test but only one completes the test, the others reverting to condition for A.C. testing. Modification. The arrangement in Figs. 8, 8a is similar to that in Figs. 7, 7a except that each inlet is connected to a vertical in two halves A and B of a primary switch, so that there are two vertical magnets VPA, VPB, only one of which is operated according to the link used, this being determined by relay Sr, which is provided for each group of 10 inlets. Sr operates when a horizontal magnet HP energizes and the link connected to the A part of switch P is occupied. Its operation causes the B link to be seized. To enable access to be given to all lines in a group of ten simultaneously, three stages of cross-bar switches are provided between the inlets and outlets, Fig. 9. 50 final selectors give access to 100 subscribers' lines through 100 P-S links, 100 S-T links and 5x20 tertiary switches, 20 different paths being provided between any inlet and any group of 10 outlets. One common selector circuit is provided for all inlets in the group, with two selector switches set under the control of the tens and units of the wanted number. The details of the system are comparable with those of Figs. 7, 7A and 8, 8A. If the called line is busy, the register recognises the condition and releases Tr, so releasing the switches. If the call is to a busy first line of a P.B.X., release of Tr restores Dr, but Er holds in series with the test relays in the register and causes the unit selector switch PF to move over the other terminals of the P.B.X. lines until a free line or the last line is encountered, when the register re-operates Tr to stop the selector and checks over lead c1 whether the line is free or busy, in known manner. Simultaneous calls. Two or more inlets may be engaged in the completion of calls simultaneously, in which case the common selector circuit operates under the control of all corresponding registers until one or more of these registers function as a result of the tens selector PF connecting the wanted tens potential, these registers simultaneously controlling the units selector PF until one or more find the wanted units potential. Other registers which may be still in the stage for tens connection are not affected by the connection of the units potentials which are lower than those for tens selections. The calls are completed in the order in which the called numbers are connected in the arc of the units selector. Combined line finders and final selectors. The three stages of cross-bar switches of Fig. 9 may be arranged to act as combined linefinders and final selectors in the manner generally described in Specification 670,252, the line-finders being controlled from a register circuit and some or all of their setting being done on a numerical basis.