Patent GB-720485-A (GB)
Title: Improvements in or relating to telecommunication systems
Inventor: PEARCE JAMES GORDON
IPC: H04Q3/00
Filed: 1952-02-08
Abstract: 720,485. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Jan. 27, 1953 [Feb. 8, 1952], No. 3336/52. Class 40 (4). In an automatic exchange in which digital information is sent in coded form over two leads, two relays, which release at different current values, are connected in series in each lead at the receiving end and means is provided at the sending end for transmitting a variable direct current over one, or the other, or both of the leads, a digit being sent by initially causing the operation of all the receiving relays and then reducing the current in one or both leads to cause one or more of the relays to be released, preceded or not by an intermediate setting of the relays. The variable current also causes the operation of one or more relays at the sending end, and the disconnection of the receiving relays from the leads, which occurs when a digit has been registered, releases the operated relays at the sending end. The invention is described as applied to the transfer of digits from the register to the selectors of a cross-bar exchange. Detailed description. The register-connector RC (Figs. 7, 8) includes two 10 X 10 crossbar switches A and B, and the leads BT to - O (Fig. 4) of the trunk relay sets 1TRS-10TRS, associated with ten trunks from a line finder/final selector such as that described in Specification 718,394, terminate on the contact units associated with the corresponding select magnets in each of the bridges 1-9 of these switches. When a trunk relay set, e.g. 1TRS (Fig. 4), is seized, relays A and B operate and ground is extended over lead RC to operate 1SM(A) and 1SM(B). Bridge magnet 10BM(A) follows, thus operating LR and connecting up CT. The operation of the relevant crosspoint of bridge BR10(A) connects the test relays 1TR-9TR to the CP wires of the first choice registers 1REG-9REG, and the test relay corresponding to the first idle register operates. Assuming 1REG (Figs. 12-19) to be free, 1TR (Fig. 7) pulls up, prevents CT from operating, and operates 1BM(A). The resulting operation of crosspoint CP1/1 of switch A extends 1TRS to 1REG, and relay 1A (Fig. 12) pulls up to the temporary loop including R1 (Fig. 4). All first-choice registers busy. No relay 1TR-9TR operates, so CT eventually pulls up, releases 10BM(A) and operates 10BM(B), whereupon the registers 10REG-18REG are tested. If one is idle, switch B switches through to it and CT is held. If, however, all are busy, CT releases and 1REG-9REG are again tested. Locally originated call. In this case the S wire of the trunk is connected to resistance earth, full earth, or positive battery in the line circuit (not shown) according as the caller is a coin-box, ordinary, or trunk-barred subscriber. Extension of the S wire to lead OT therefore results in the operation of CCB (Fig. 16) alone, CCB and ORD, or CCB, ORD and BTR as the case may be. The operation of 1A brings up 1B (Fig. 17), which operates IP (Fig. 18) and returns earth over lead BH to hold 1BM(A) (Fig. 8), and operates 1CA (Fig. 18), the first of six relays 1CA-1CF forming an impulse counter. TTO (Fig. 15) and C (Fig. 17) follow to initiate a forced release timing period, and to revert dial tone respectively. In all cases, CCB brings up BB (Fig. 17), which grounds lead CN, thus operating CO (Fig. 4) which releases 1SM(A) and 1SM(B), connects the P and OT leads of the register to the P and S leads respectively of the first group selector, and extends the calling loop directly to the register. Magnet 10BM(A) is thus released and the register-connector is available for other calls over 2TRS-10TRS. Incoming calls from exchanges sharing a linked numbering scheme with the local exchange. The digit which has been dialled at the remote exchange to gain access to the local exchange needs to be stored in the register. For this purpose the P wire of a register. connector serving incoming trunks from such an exchange is connected to the relevant leads of P/T2-P/T9 or P/F2-P/F9 according as the subsequent impulses are to be 10 I.P.S. (33<1>/3 per cent make) or 30 I.P.S. (50 per cent make). Accordingly, the corresponding one of the eight relays AW-AZ and BW-BZ (Fig. 12) operates with either TIC, for standard impulsing, or FIC for high-speed impulsing. The corresponding select magnet of switch R, e.g. 9SM(R) (Fig. 17), is thus operated together with 1BM(R) (Fig. 18) to store the digit. Relays AS and CS (Fig. 17) pull up followed by BB and MF, whereupon the operated digit relay, e.g. BZ, restores and releases the select magnet, whereupon CS relapses and BS operates. Relay D (Fig. 12), operated by TIC or FIC, disconnects dial tone. Calls incoming from exchanges not sharing the linked numbering scheme. The registerconnector P lead is wired to lead NT or NF as the case may be, so that NHD comes up with either TIC or FIC to bring up BB. The digit dialled to reach the local exchange is not stored. Caller dials wanted number. Relay 1A repeats the impulses to 1CA-1CF, CO coming up for digits 6-0. The release of C at the end of the train operates the corresponding select magnet over contacts of 1CA-1CF and CO. If the call is not an incoming one from an exchange sharing in the linked numbering scheme, this operation, of say 6SM(R), brings up AS and 1BM(R). CS, which follows, restores the counting chain, 6SM(R) releases and BS operates; the consequent relapse of CS bringing up 1CA followed by C. The second digit is stored on bridges 2 and 10, AS is shunted down and CS operates to clear the counting chain as before. The contacts of bridge 10 are used to supplement those of bridge 2 as regards discriminatory functions described later. The register may store up to ten digits, the tenth bringing up TD (Fig. 18) which connects up the relevant marking lead 1DC-10DC (Fig. 15), the select magnet being held for this purpose. Cross-connecting fields ASF, BSF, CFS (Fig. 19). The first of these is used to determine from the first, second, or third digit the number of digits to be stored, strappings to terminals 1DT-9DT ensuring that pulsing out will cease after one to nine trains respectively. It is arranged that for local calls and for unit-fee calls to be extended over 30 I.P.S. junctions, the start of retransmission awaits the storage of the penultimate digit, SX coming up over the appropriate select magnet contact, e.g. 4BM3(R), to initiate sending. Contacts of switch R which correspond to spare codes are wired to tag SC (Fig. 15) to bring up relay NU. The second field BSF determines from the routing digits the metering fee, by means of jumpers to tags RMT (Fig. 12). KMT1-RMT6 correspond to fees chargeable once only or at 3-minute intervals, and RMT4D-RMT6D to fees chargeable at 1¢-minute intervals. As either MB, TIC, or FIC will be operated on an incoming call, the metering field BSF is disabled for such calls. Strappings in the third field CSF to tags 20-27 bring up combinations of OTS, TS, AMF, OSR, and OTR to determine the type of impulsing to be used, whether unit-fee or multi-fee metering is to take place, and from which rank of selectors the outgoing junction is taken when 101.P.S. impulsing is to be used. In particular OTS comes up for 30 I.P.S. impulsing, TS for 10 I.P.S., AMF to indicate multi-metering, OSR for second selector junction, and OTR for third selector junction. Call to local subscriber. It is assumed that the four digits required are stored. Immediately the first digit (4-8) is stored, OTS (Fig. 19) pulls up; and when the third digit is stored, DD and SX come up over field ASF. Relay TR (Fig. 16) is thus connected to lead OT and, if the first selector control equipment is idle, it pulls up and grounds the P lead. This operates 1SM(C) (Fig. 5) of a three-bridge crossbar switch C, followed by 1BM(C) (Fig. 9); so that leads + O, - O of the register are extended to the code-receiving relays W,X and Y,Z respectively. Transfer of digits. The operation of TR also brings up SS (Fig. 17), whereupon SZ, HA and HB follow and connect the grounded lowresistance windings of SCA and SCB (Fig. 16) to +0 and - 0 respectively, thus sending the " seize " signal. Relays W, X, Y, Z (Fig. 9) pull up to this signal, ST follows and brings up STA and AA, the latter placing the select magnets 1SM(C)-10SM(C) under control of W, X, Y, Z, and removing battery from lead OT. SZ (Fig. 13) also operates SA in the counting chain SA-SF (Fig. 16) which extends a marking ground over bridge common 1A (Fig. 15) to mark the digit lead 1DC-10DC corresponding to the first digit. Assuming the first digit to be 8, relay OFA (Fig. 13) (relevant to all digits over 5) is operated, thus holding HB and operating LA. The operation of SCA and SCB when the seize signal is sent brings up SCC (Fig. 13), whereupon HA and SZ relapse, so that SB operates in series with SA, and AOF (Fig. 12) is connected up. Relay SCA is released by HA, which connects the high resistance NR to lead +0 and full earth to -0. These conditions constitute the " over 5" signal to which W, Y, Z (Fig. 9) hold, bringing up OF which ensures that the succeeding digital signal is effective on 6SM(C)- 10SM(C) in place of 1SM(C)-5SM(C). Relay NR (Fig. 16) operates and SCB, SCC relapse. The operation of AOF disconnects OFA (Fig. 13) and extends leads 6DC-10DC to LA, LB, HA. The marking on 8DC holds LA and brings up LB, so that when OFA releases, NR is connected to - 0 as well as to +0 and the " digit 3 or 8 " signal (resistance earth on both leads) is sent. Relays X and Z (Fig. 9) hold to this signal, so that STA falls away and operates 8SM(C), 8SM(AS), and 8SM(BS) (not shown). Selection of outlet. The bridge magnets 2BM(C) and 3BM(C) are thus operated and STA is re-operated. The cross-points corresponding to 8SM(C) in bridges BR2 and BR3 of switch C extend the T leads of the eighth group of twenty first selector outlets to the bridge commons. If any link is busy, the operated secondary switch bridge magnet disconnects the correspond