Patent GB-679544-A (GB)
Title: Improvements in or relating to telecommunication systems
IPC: H04Q3/42
Filed: 1949-02-03
Abstract: 679,544. Automatic exchange systems. MERCER, R. Feb. 1, 1950 [Feb. 3, 1949], No. 3039/49. Class 40 (iv). In an automatic exchange in which a plurality of stages of static multiposition switching devices give access to a calling line and a plurality of similar stages give access to a called line, there is provided means for seizing an idle one of a plurality of common control equipments on the initiation of a call, means for rendering available individual characters designating the calling line in the seized common control equipment, means for storing the individual characters designating the called line in said equipment and means forming a component part of the seized common control equipment for selecting and operating multiposition switching devices in tandem of each plurality, each device being operated in accordance with one of said individual characters to establish a connection. A static multiposition switching device is defined as an assembly of contact devices, electronic valves, triggered gas discharge tubes or other devices each individually capable of being selected to set up a connection, the operative elements being located in various positions which are themselves selected in accordance with the selective action desired. In the two-digit embodiment disclosed the static multiposition switching devices comprise relays and only three relays are shown for each such device, namely the first, second, and last. The characters 1 and 2 are used to designate devices corresponding to digits 1 and 2, and A to designate those corresponding to the highest value digit. General arrangement of system, Fig. 1. A maximum of A<SP>2</SP> subscribers is served the lines being shown as 11-1A, 21-2A ... A1-AA. In addition to the usual line and cut-off relays jointly represented by crosses on the line CL, the crosses on the lines DOa, DOb ... DOn represent relays giving access to impulse responding equipments 1Ra, 1Rb ... 1Rn, and those on lines 1P, 1Q, 1X, 2P, 2Q, 2X, AP, AQ, AX relays giving access to or from the lines with which they are associated from or to battery feed equipments BFP, BFQ, BFX. An impulse responding equipment receives the dialled digits, selects an idle battery feeding set having access on both the calling and wanted line sides to an idle set of relays associated with the calling and wanted lines, and converts the received impulse trains into a code suitable for the selection of a relay of a static multiposition switching device corresponding to the dialled impulses. A battery feeding set comprises a Stone bridge or the like, and means for ringing a wanted line if idle, the busy indication being given from the impulse responding equipment. It also has associated with it two chains of relays each corresponding in number to the maximum value of the first digit of subscribers' numbers, one chain on the calling and the other on the wanted side. Normally, 2A outlets are provided from each battery feeding set, but economy in outlets may be obtained by suitable multipling as illustrated in Figs. 2a, 2b (not shown). Operation: General. Assuming that calls have already been set up from 11 to 12 via 1P, CIP, BFP, W1Q and 1Q, and from 1A to AA via 1X, C1X, BFX, WAP and AP, it is desired to set up a call from 22 to Al. The caller lifts his receiver and a control is passed via CL to an idle impulse responding device, e.g. 1Ra, whereupon over DOa the line 22 is extended to 1Ra and dialling tone is transmitted. The digits A, 1 are then dialled and are registered on two relay registers. Tests are made cyclically over common lead A (1st digit of wanted party), and common lead 2 (1st digit of calling party) to determine the condition of the connecting relays of groups A and 2, and these leads in conjunction with common lead BFTL, over which is determined the condition of the battery feeding sets, control the connection of 1Ra to a battery feeding set over which the call may be set up. 1Ra is therefore switched through to BFQ and at appropriate instants in a cycle impulses are transmitted to operate successively WAX and the relay corresponding to line A1. At the same time impulses are transmitted as determined by the calling line to operate successively C2Q and, when the called line is reached and found idle, the relay corresponding to line 22. The connection is completed when 1Ra and the relay connecting DOa to 1Ra are released. Detailed operation, Figs. 3-12. When subscriber 11 (Fig. 3) lifts his receiver to initiate a call line relay LR11 comes up and grounds the common start lead SL which extends to the first idle impulse responding equipment, e.g. 1Rn (Fig. 9). Relay SRn operates and connects ground to CCL and battery to BLn, whereupon Rn11 (Fig. 4) pulls up over back contacts of line relays LRAA to LR12 and front contact of LR11. Rn11 locks up in series with CO11 which operates and line 11 is extended to relay An (Fig. 9). An pulls up followed by Bn and SRn relapses. Dial tone (from a source not shown) is reverted to the caller who dials the wanted number -AA. The break " of the first impulse operates Cn and FDln partially (" X" contact only) and at the end of the impulse FD1n operates fully. The next impulse brings'up FD2n which releases FDln until on the A impulse FDAn comes up and releases FD(A-1)n (not shown). Relay COn which operates partially on the first impulse, operates fully at the end of the train and extends the impulsing circuit over ILSD for the second digit which operates SD1n ... SDAn (Fig. 10) in like manner. Relay Cn re-operates during the second train completing a circuit over E1n to operate LDn (Fig. 11) partially. At the end of the train LDn operates fully and connects battery to lead RSL. On the operation of Rn11 the identifying lead 1LTn is connected to bus-bar lead 1E of cable'BCE. There are 2A+2 " E " bus-bar leads to which earth is connected at 2A+2 separate instants in a cycle and to 2A+2 corresponding " B " bus-bar leads battery is similarly connected, these connections being effected by the cams shown in Fig. 12. The impulses are of about 20 m. secs. so that if A=10 the duration of a cycle is about 440 m. secs. At instant 1 in the first cycle after Rn11 operates, relay CFDln (Fig. 9) operates over leads 1E, 1B to register the first digit of the calling line number. The next operation is to find an idle battery feeding set having idle outlets for first digit 1 on the calling side and first digit A on the wanted side. Group test leads GTL1, and GTLA are used to test for the idle outlets and BFTL for the battery feeding sets. The hold relays HP, HQ, HX (Figs. 6, 11) connect bus-bar leads PE, QE, XE respectively through rectifiers to BTFL if the corresponding sets are busy and relays CIP, CIQ, CIX, WIP, WIQ, WIX similarly connect leads PE, QE, XE to GTL1 if the respective outlets for digit 1 on either the calling or wanted side are busy. GTLA is marked in like manner by CAP, CAQ, CAX, WAP, WAQ, WAX. Assuming BFP and BFQ to be busy on calls from 12 to 2A and Al to 22 respectively then PE or 1E will be connected to BFTL and GTL1; QE or 2E to GTL2, BFTL, and GTLA; and XE or AE to GTL2. The selection of BFX (having free outlets via C1X and WAP) is effected by the operation of LDn (Fig. 11) at the end of the second impulse train over back contacts of Xn, Qn, and Pn to ground on HLn. The right-hand windings of Pn, Qn and Xn are connected between the lead RSL and leads PE, QE and XE respectively. Lead RSL is connected to resistance battery by LDn; over rectifier TLFR and front FDAn to lead GTLA to which QE is connected; over rectifier TLCFR and front CFD1n to GTL to which PE is connected; and over rectifier BFTR to BFTL to which PE and QE are connected. Consequently at instants P and Q relays Pn and Qn respectively are short circuited, but at instant X relay Xn operates, locks to HLn and extends leads HE, COL and WOL to BFX. Lead WOL which is connected over the lower winding and back contact of WTn (Fig. 10) to the first digit operating lead FDOL and thence over front FDAn to bus-bar lead AE is extended by Xn to one side of relays W1P, W2P and WAP (Fig. 12). As the other side of WAP is connected to bus-bar lead AB this relay operates in series with WTn at instant A in the cycle. WTn locks to HLn and transfers WOL from FDOL to the second digit operating lead SDOL, and WAP extends the outgoing side of BFX to cable AP associated with relays A1P, A2P and AAP (Fig. 9), WOL being thus connected to one side of each of these relays. With SDAn operated (2nd digit A) lead A+AE is connected to the other end of WOL (Fig. 10) and as the other side of relay AAP is connected over resistance A+AR to lead A+AB, AAP operates provided line AA is idle. Called line busy. If AA is busy, one of the other AA relays is already operated and earth is extended at instant A+A from lead A+AE over lead GL to the end of A+AR remote from the battery connection to lead A+AB, so that AAP remains unoperated and at instant 2A+1 busy relay BRn (Fig. 10) comes up over front WTn and back BRn and connects up busy tone. The calling party then hangs up, whereupon An and Bn fall away to initiate release. Connection of BFX to calling line. This is effected by the operation of C1X (Fig. 11) and 11X (Fig. 5) as explained below. However, to prevent Rn11 from being released by 11X before the busy test has been completed, the operating lead COL is connected over a front contact of WTn and a back contact of BRn. Assuming BRn is not operated, COL is connected to the identifying lead 1LTn to which Rnll has connected lead 1E, so that at instant 1 earth is applied to one side of relays C1X, C2X and CAX and since 1B is connected to the other side of C1X that relay operates, locks to HE, and extends COL over cable 1X to relays 11X, 12X, 1AX. Relay CTn (Fig. 10) operates with C1X and transfers COL from 1LTn to 1LUn for the units digit of the calling line. As Rn11 connects A+1E to 1LUn and as A+1B is connected to the other side o