Patent GB-735109-A (GB)
Title: Improvements in automatic telephone systems
IPC: H04Q3/00
Filed: 1952-04-04
Abstract: 735,109. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. April 4, 1952 [April 11, 1951], No. 8689/52. Class 40 (4). In an automatic exchange system switches of a first stage have access to switches of a second stage and also via overflow outlets to other switches of the first stage, such other switches only being selected if they give access to a free second stage switch. General description. A selection stage SL, Fig. 1, serving 500 subscribers P comprises a combined first line-finder/final selector switch MCC accessible to a selection stage MC on the one hand and giving access on the other to a secondary line-finder MCH. A line-finder MCH gives access to a feed-bridge JE which seizes a register EN over switch ME. The feed-bridge gives access to a group selection stage SG comprising primary and secondary stages MP, MS giving access to outlets leading to the wanted 500s group SL in which the selector MC gives access to the wanted final selector/first line-finder MCC. Each switch is associated with control circuits ORCC, ORCH, ORC, ORP, ORS. A calling subscriber may be served by either of two ORCC control circuits, -each of which may operate in conjunction with two ORCH control circuits for connecting the calling subscriber P to a feed-bridge circuit JE via the switches MCC, MCH. The feed-bridge JE seizes a register EN which registers the digits which are then translated into a group of two digits designating the wanted 500 group and a group of three digits designating the identity of the line within that group. The first group of digits is transmitted to the control circuit ORP which seizes a secondary selector having a free outlet in the wanted direction. The second digit is then transmitted from ORP to the control circuit ORS to control the seizing by the secondary selector of a free outlet to the wanted 500 group. A circuit ORC associated with the selector MC then receives the last three (translated) digits and repeats them to ORCC which marks the wanted subscriber P and ORC and ORCC then complete the connection over switches MC, MCC. Fig. 2 illustrates the trunking within a 500-line group. Each subgroup of 50 subscribers P are served by two half-switches MCC, MCC1, two half-switches e.g. MCC, MGC<SP>1</SP>, making up a complete switch having a split multiple. Each group of 500 lines may be connected to feed bridge circuits JE by four switches MCH, MCH<SP>1</SP>, MCH1 and MCH<SP>1</SP>1, each having 50 outlets which are divided into ten groups of five. Each switch MCC receives a group of five from MCH and a group of five from MCH<SP>1</SP>. Switches MCC1 are connected similarly to MCH1, MCH<SP>1</SP>1. Group selector outlets SG are connected to the 500-line groups via switches MC, MC<SP>1</SP>, MC1, MC<SP>1</SP>1. The outlets of each of these switches is divided into 10 groups of four normal outlets and one group of ten overflow outlets. Each switch such as MCC receives four outlets from MC and four from MC<SP>1</SP>. Switches like MCC1 are connected similarly. The ten overflow outlets let from MC, MC<SP>1</SP> are commoned in pairs and are connected to five selectors in each of the switches MC1, MC<SP>1</SP>1. The overflow outlets let1 are similarly connected. Operation of line-finder. Relay A, Fig. 4, operates to the calling subscriber's loop and brings up M in one of two control circuits such as ORCC. Relay M brings up KC if the control circuit is not in use at that moment. Thereupon the relay Pd appropriate to the 25s subgroup of the calling subscriber operates Gc in two control circuits such as ORCH, the Gc relays characterizing the 50s group of the calling subscriber. Relays Gc complete circuits for two Tcc relays, one in each control circuit ORCH, one of which operates, brings up Dsc and Tbc and connects up five Tac relays to backward-going r-wires over contacts gc2. Available finders CCN energize the corresponding Tac relays one of which operates. A circuit is thus completed for the selecting magnets Sc, Spc corresponding to the tested free finder in the wanted 50s group. Relay Tcc grounds ft7 to bring up a relay Ad characterizing the 25s sub-group of the calling subscriber. Magnet Sf, characterizing the level of the calling subscriber in its 25s sub-group, is thereby operated and connects into its circuit two Ed relays corresponding to two 25s subgroups. Arrangements (not shown) are provided to ensure that only the Ed relay corresponding to the sub-group of the calling subscriber is operated. The relay Ed then brings up the corresponding Spf magnet which, with Sf, determines the identity of the calling subscriber. It is arranged that the magnets Sp, Spf serve two adjacent 50s groups of lines. Each of the 20 links JE to which the switches CHS have access is characterized by a combination of one out of five Ua relays and one out of four Ga relays. One Ua and one Ga relay are normally operated corresponding to a free link having associated with it. If the link becomes busy battery is removed from wire t by the operation of Ca or La. Likewise if a link has no free register available to it, Cha releases to remove this battery. In either case the corresponding Ua relay cannot operate. If all five Ua relays are unoperated a cyclically operating device Altc is stepped to bring. up a second Ga relay corresponding to a further set of five links. If a free link associable with a free register is available in this set a Ua relay operates to stop Altc. Otherwise Altc continues to step until a Ua relay operates. Relay Coc operates over wire ft10 and brings up the magnet VF over the v-wire, and release-guard relay Ca in ORCC over ft19. Magnet VF switches the calling subscriber through to CHS and operates the subscribers' relays C and A over the t-wire in series with a second winding of Dsc which releases by differential action. Magnet VF opens the r-wire circuit to busy the outlet. Relay C releases M. Release of Dsc operates the control magnet VC determined by the operated relays Ua, Ga to complete the switchthrough to the link JE. Relay C releases Pd which initiates the release of ORCC and also releases Gc to initiate the release of ORCH. Seizure and setting of register. Relay La operates to the calling subscriber's loop and, provided there is a free register EN, reverts holding ground over the v-wire to hold magnets VC, VF. The control circuit ORCE serves to connect 50 links JE (divided into 2 groups of 25) with one of 8 register-senders EN. Each register-sender has two hold magnets associated with it, one for connection to each of the 25s sub-groups. Relay LA operates relay PE associated with the appropriate link sub-group. Pe brings up a relay Ae also associated with the 25s sub-group provided its mate for the other sub-group is not operated. The Ae relay energizes eight chain-connected Te relays, one of which, corresponding to a free register, is operated. The Ae relay operates magnet Se which is indicative of the identity of the calling link in its sub-group of 25. Magnet VE corresponding, to relays Te, Ae, then comes up to connect the link to the register EN. Link supervisory relay CA then comes up over the t1 wire of the switch CHE and locks over a circuit ultimately controlled by called and calling parties' loops. In the register, Ee operates to the calling subscriber's loop and brings up Le, which busies the register. Relay Ca releases La, Pe, Se and Ae; Le releases Te. The digits are then received and registered in EN in the usual manner. The register translates the digits into suitable group designating digits and transmits them over the a, b and c wires in the form of combinations of polarities. Selection of 500s group. One circuit ORP is provided for controlling the connection of 10n links JE to the required 500s group via switches SEP, SES. Subsidiary control circuits ORS are provided for the switches SES. The link JE grounds wire v to operate one of the n Pp relays indicative of the group of ten to which the link belongs. The Pp relay brings up a common relay Cp if the control circuit is free, and a chain-connected Ap relay corresponding to the operated Pp relay is operated. The ap5 contacts are multipled in pairs on the Bp relays which indicate the level of the link JE in its tens group. The appropriate Bp relay thus operates. The n group of links are divided into m sets each set having access to the same group of outlets. Each set has a characterizing Ep relay operated by contacts ap7 of such of the n Ap relays as characterize 10s groups which belong to the set. Relay Ep operates Tbp which brings up Tdp followed by Tcp. The latter at its 5 tcp1 contacts prepares the circuits for 5 Tap test relays. The first two translated digits are received on two Dp relays for the first digit and on four Up relays for the second digit. Of the four combinations of the operated and non-operated states of the Dp relays two are used for routing inter-exchange calls and two for local calls, i.e. each denotes a group of 5000 lines. The level within the 5000 group of the 500 lines in which the called subscriber resides is received on the four Up relays. Relay Lp operates in the holding circuit of the Up relays to bring up relay Gp corresponding to the first received digit and relay Chp corresponding to the second received digit. Lp releases Cp. The device Altp closes contacts altp1 ... altp5 cyclically and the four contacts gp1 are multipled to these to give 20 leads fp66, each of which may be used to designate an outgoing sub-group of 5 lines. As there are 50 outlets from the selector SEP not all of these leads are used. As described, the first group of 5000 lines is allocated 20 outlet lines, i.e. four groups represented by four leads fp66. The remainder of the groups are allocated 10 outlets, i.e. two groups represented by two leads fp66 each. With altp1 closed, relay Np corresponding to one of the required sub-groups operates and also one of 10m relays Fp whic