Patent GB-744129-A (GB)
Title: Improvements in or relating to circuit arrangements for use in telecommunication systems
Inventor: MERCER RICHARD
IPC: H04Q3/00
Filed: 1951-04-03
Abstract: 744,129. Exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd.. March 25, 1952 [April 3, 1951], No. 7665/51. Class 40 (4). Crossbar switches are used as primary and secondary finders for linking a calling line with a free impulse responder in a system using route selection as described in Specification 656,559. Mechanically generated cyclic pulses are used for marking and operating switches as described in Specifications 652,881 and 665,129. The line group to which a calling line belongs is first registered on a crossbar switch before a route is selected, The circuits are described in detail With reference to Figs. 5 to 16 (not shown) but may be followed by reference to Figs. 1 to 4. In the drawings, a square with diagonals represents a set of contacts in a crossbar switch. A square without diagonals represents a prepare magnet in a hold magnet as indicated by a prefix PM or HM. Line groups 11-1A, 21-2A, A1-AA, Fig. 1, are shown allotted respectively to primary finders P1, Q1, X1 ; P2, Q2, X2; PA, QA, XA. The primary finders are connected to secondary finders, Fig. 2, so that primaries P to PA have access to secondaries Pp to Px, primaries Q1 to QA have access to Qp to Qx &c. each secondary finder identifying a path or route with the same reference. When the receiver is lifted at station 11, the tens group 1 (assuming A is 10) is registered on a crossbar TR. Marking pulses IE (ground at the first instant of each cycle) are applied to leads T1 and U1 to mark the tens and units digits. Ground is connected. to hold lead HL and prepare magnet PMTR1 operates in TR to register the tens group 1. The first free hold magnet HMTRa of a chain HMTRa ... HMTRn operates to connect on idle relay set REa individually associated with the hold magnet. The magnet HMTRa holds for the time being to the lead HL. The relay set then carries out a test to find a free route. Battery is applied to test lead CTLa in REa over a contact of the hold magnet HMTRa. Battery is applied in pulses each of which is long enough to embrace a whole cycle Pp ... Xx. To avoid simultaneous testing by the relay sets, REa . . . REn battery pulses are applied to each in turn. The common test lead is connected to test lead TLIFa which is connected through the register TR to test lead TLIFI. Test lead TLIFI bears markings indicating the routes which are not available to the first tens group through primary finders P1, Q1, X1. If Q1, for example, is busy, pulses QpE, QqE, QxE are applied to TLIFI although some of the routes Qp, Qq, Qx may not be busy. Test lead TL2F bears busy markings indicating what individual routes are busy. Any busy marking on CTLa short-circuits a test relay which then cannot operate. The test relay operates at the first instant, say Pp, in which no busy marking pulse is found on lead CTLa whilst battery is connected to it. The prepare magnet PMPp in RF is marked with battery at instant Pp in each cycle and operates when the test relay connects ground to OLRF at instant Pp. Hold magnet HMRFa, which is individual to the relay set RFa follows the test relay after a delay and a connection is extended from REa through the route finder RF. In the secondaries, a prepare magnet PM2F1, individual to the tens group 1, is operated by the test relay over contacts of the tens register. Hold magnet HMPp individual to the route Pp is operated by ground on HL which is now extended from the calling line equipment through the route finder RF. The prepare and hold magnets of the primary switch P1 remain to be operated. Lead U1 marked with pulses 1E is extended from the calling line equipment through TR and REa to operate-lead OL which is extended through the secondary switch Pp to prepare magnet PM1 which is marked with pulses 1B (battery at the first instant of each cycle) and which operates. The lead OL is also extended to hold magnet HMP1 which is slower to operate than the prepare magnet and holds to the extended lead in series with the line cutoff relay. The calling line is now extended over leads SL through the primary and secondary switches P1, Pp to the relay set REa in which a line relay responds to any impulses dialled. The line cut-off relay removes the holding ground and the marking pulses on T1, U1 and the hold magnets are now held by ground provided in the relay set REa. Specifications 679,544, 744,121, 744,122, 744,123, 744,124, 744,125 and 744,126 also are referred to. Reference has been directed by the Comptroller to Specification 665,129.