Patent GB-675088-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H01H67/12
Filed: 1948-04-23
Abstract: 675,088. Automatic exchange systems. STROMBERG-CARLSON CO. April 23, 1948 [April 23, 1947], No. 11297/48. Class 40 (iv). In a system which employs as line finders and selectors two co-ordinate switches whose wipers move in front of and then into a bare wire multiple, incoming trunks are wired to the level or row of the line-finder banks opposite which the wipers normally stand so that they may be reached by one direction of motion. A 1000-line system is described with provision for party-line working and P.B.X. hunting. The group selectors may be arranged for digit absorption on certain levels. The drawings are arranged as shown in Fig. 2. Switch construction, Fig. 1. The carriage 1 on which two pairs of wipers 2, 3 are mounted is moved along a shaft 5 in the X direction by a double-cut tubular gear 4 which is driven by a magnet 7 through a pawl and ratchet 10 and gear 6. The gear 4 is then rotated step-bystep by a magnet 15 and acts through pinions 21 and racks 20 to drive the wipers in the Y direction into the selected level or row of the bank, which is provided by a bare wire multiple. The position of the wipers is indicated on scales 17, 18. During the X movement, auxiliary wipers 11, 11a are advanced by means of a pinion 12 and rack 13 into a separate bank. X and Y off-normal springs 25, 26 are provided as well as overflow springs 27 which close on the eleventh step in either direction. Upon operation of the release magnet 30, the wipers and carriage are returned by spring action. The switch may be provided with eleven levels or rows, the first or normal level being reached without movement in the X direction. Line circuit, Fig. 3, finder, Fig. 4, and allotter, Figs. 11-13. Line relay LL grounds start wire LST and marks the calling line in banks X, H. Start relay AS1 energizes in the allotter followed by AS2, and line relay SC, Fig. 5, of the allotted finder-selector link pre-energizes over wire PI. Link-idle relay ALI falls back, AD pulls up, and magnet FX steps the finder until AX energizes over the auxiliary X wiper. Relay AD now falls back and magnet FY is operative until AA energizes over the H wiper. Switching relay FCT energizes over wiper S in series with cut-off relay LCO, which connects lock-out relay LLO in parallel, and start wire LST is opened to release AS1, AS2, whereupon the allotter advances to the next idle link and AL1 re-operates. Two allotters are provided for each 100-line group and each normally serves half the group. Link-busy relays ALB, A<SP>1</SP>LB are operative as long as there is an idle link in each half group, and if either of these relays falls back the allotter corresponding to the other serves the whole group. If all links are busy, ALB, A<SP>1</SP>LB are both back and a tone is returned by way of the line circuit. Provision is made for applying coin box tone to wire S to notify an operator. Group selector, Figs. 5, 6. Line relay SC connects up release relay SD and dialling relay SXD. Dialling tone is sent back and dialled impulses are repeated to magnet SX and SXD, and relay SH pulls up at the first step. The relapse of SXD at the end of the train makes a hunting circuit for magnet SY by interaction with SH which after the first step in the Y direction is connected to test wiper S. Test relay SMT, which is connected to terminals of the XX bank indicating unrestricted levels, is short-circuited on busy outlets, and when an idle outlet is reached energizes in series with SH and switches through. On dead levels however, there is no connection in the XX bank and the selector stops after one step in the Y direction and sends NU tone. On restricted levels the operation is similar except in the case of incoming trunk calls which are permitted access to all levels. Connector, Figs. 7-9. Line and release relays CC, CD energize followed by CXD, CYD. The impulses of the tens and units digits are repeated to magnets CX, CY, changeover being effected by the release of CXD. Relay CBT energizes over wiper S if the wanted line is busy, and is locked by the relapse of CYD, busy tone being reverted. If the line is idle, the relapse of CYD connects up CCT, which energizes over the cut-off relay, and CSD, which allows the setting of a switch CS by the final impulse train to select over bank T or R a frequency-code-ranging circuit. Ringing takes place on one leg or the other on the relapse of CSD, and, upon reply, ring-trip relay CRT pulls up followed by back-bridge relay CA. Revertive calling by means of revertive call circuit, Figs. 15, 16. This is reached when the group selector receives the digit 9, and the calling party then dials the digits representing the wanted station and his own station on the party line. Line and release relays RC, RD energize followed by R1SD, R2SD. The two digits step switches R1S, R2S respectively, R1SD goes back after the first and R2SD after the second, and R1SD then re-operates. The calling party now hangs up and the release of RC connects up ringing relay RR, whereupon R1SW, R2SW operate alternately over pulse wires 78, 79 to ring both parties. Upon reply, RRT responds and brings about release of the revertive call circuit and of the selector; line relay LL, Fig. 3, re-operates and holds lock-out relay LLO. Revertive calling by dialling of directory number. In this case, the connector, Figs. 7-9, is provided with the circuits in rectangle E and wiring X is used. When the wanted line is found to be busy, the operation of CBT energizes CRC which applies ground to test wiper S, with the result that CSL connected to the incoming test wire is short-circuited on a revertive call but operates on an ordinary call. Relay CRD also energizes, locks and, provided CSL is back, holds release relay CD independently of CC. The calling party dials the final digit and busy tone is returned. When the calling party hangs up, CC and CRC releases, connects up switching relay CCT and the wanted party is rung. Upon reply, CD is disconnected by CRT and brings about release of the connector and preceding link, the line being locked as mentioned above. A separate switching relay may be provided for operation on revertive calls. Incoming trunk calls. Incoming trunks are wired to the normal level of the finders, and the line circuit of calling trunk grounds trunk start wire TST, Fig. 12, to operate ANL which connects up start relay AS1, Fig. 11. In consequence, the circuit of magnet FX, Fig. 4, is opened and the finder steps immediately in the Y direction. The connection of wires 69, 70 at off-normal contacts FXON allows the selection of restricted levels of the group selector. Digit absorbing. When the selector, Fig. 6, is provided with the circuits in rectangle D and wiring M, and a digit to be absorbed is received, relay SDB energizes over wiper XX and the wire S, locks and connects up release magnet SZ. In normal position, SAB pulls up and renders further operation of SDB ineffective. The digit 1 is always absorbed by direct operation of SZ over wiper XX. Conversation timing. When any call is switched through, relay BCTS, Fig. 14, is operative over wire BCTS and relays BPT1, BPT2 are controlled by pulse wire OTP to apply ground periodically to the XX terminals of the finders and connectors. In the connector, Figs. 7-9, these pulses step switch CS (which is restored when CRT comes up) from the time that CA energizes. Warning tone is given in positions 7 and 9 of bank C and the connection is forcibly broken down by re-operation of CSD in position 10. If either party is privileged, the corresponding XX terminal is grounded continuously and CS cannot step. P.B.X. hunting. The circuits in rectangle F, Figs. 8, 9, are included and wiring C is used. The first and intermediate lines of a group are marked in the H bank by resistance battery, and the last line by direct ground. Relay CTH energizes on the first line, and if busy relay CBT is operative makes a stepping circuit for magnet CY by interaction with CPA. During hunting, CTH holds over its windings in series, CXD and CYD being up, and CBT is held as long as busy lines are encountered. On the last line, however, the upper winding of CTH is short-circuited and current in the lower winding releases the relay and opens the stepping circuit. Busy tone is sent if this line is busy. Irregular operations. If a finder-selector link is held for an undue time without impulses being received, relay SPT, Fig. 6, energizes over wire OPU which is periodically grounded at interrupter 71, Fig. 14, and connects up wire S to wire OH, from which holding ground is removed at interrupter 72, Fig. 14, after a further period. Cut-off relay LCO, Fig. 2, falls back and line relay LL re-operates and holds lock-out relay LLO, an alarm lamp 81 being lighted. Relays CPT, Fig. 7, and RPT, Fig. 16, fulfil a similar purpose. If the finder fails to find the calling line, it operates overflow contacts and thus steps on the allotter. Relay APT, Fig. 11, also causes advance of the allotter if the calling line is not found on account of failure of the finder. Each operation of AX is counted over wire PC. Timing relays SPT, CPT may be omitted from the selector and connector, and relays may be provided in the common equipment, Fig. 14, for giving an alarm.