Patent GB-959578-A (GB)
Title: A telephone system comprising a main exchange and at least one satellite exchange
IPC: H04Q3/00
Filed: 1960-11-14
Abstract: 959,578. Automatic exchange systems. TELEFONAKTIEBOLAGET L.M. ERICSSON. Nov. 14, 1960 [Nov. 12, 1959], No. 39115/60. Heading H4K. A satellite exchange uses switches of a crossbar type which are duplicated at the main exchange as if all the satellite subscribers were connected to subscribers outlets at the main exchange in the same way as main exchange subscribers, the satellite having an identifier which transmits or receives the calling or called subscriber's identity to or from the identifier at the main exchange so that the satellite switches may be set up in the same way as the duplicate switches at the main exchange. General description.-The system described uses code-bar relay selectors, each of which has ten bridges, the ten corresponding inlets to which have access by means of triple or quadruple group working to 40 or 50 outlets depending en whether a stage requires a fourth wire or not. As shown schematically in Fig. 1, the main exchange comprises a first stage of 16 selectors SLA serving 800 main exchange subscribers and including 4 selectors MSLA which duplicate the 4 selectors SSL4 at the satellite which serve 200 subscribers. The 40 inlets to the SSLA selectors are connected by as many j junctions to the main exchange where they are connected in common with the 40 inlets of the selectors MSLA to outlets of the second stage of two groups of 5 selectors SLB arranged in pairs giving access from 20 inlets to a commoned 40 outlets. State SLB therefore connects any one of 50 originating relays sets SNR or any one of 50 terminating relay sets LKR to any one of the 200 inlets to the first stage comprising SLA, and MSLA and SSLA combined. Each SLB selector has access to two bridges of any SLA, MSLA, selector. Associated with the satellite is an identifier SIDS having access over codemarking wires to the identifier MIDS serving the selectors SLA and MSLA at the main exchange. Battery for the satellite is fed over separate wires from the main exchange. A marker SLM controls connections over the first and second selector stages and also controls a stage SLC the outlets of which give access to terminating relay sets LKR and the inlets of which are connected to the outlets of group selector stages GVA, GVB, and to lines incoming to the exchange. The identifier IDC associated with the stage SLC co-operates with a code receiver and translator KMS which sets up the marker SLM for wanted subscribers. A marker RSM and register REG are associated with the originating relay sets and an identifier IDG, code receiver KMG, and marker GVM, serve the group selectors; none of these is described in detail. Selectors.-Fig. 3 shows a bridge from each of the first and last of the selectors SLA and MSLA to illustrate the allocation of outlets to subscribers. Each bridge has 12 row wires co-operating with seventeen columns of contact springs, columns 14 to 17 selectively connecting the bridge inlet a, b, and c, wires to any one of the four sets of three row wires, 1 to 3, 4 to 6, 7 to 9, or 10 to 12. Subscriber's outlets are distributed over the contact sets of columns 1 to 13 according to the numbering scheme shown, column 13 having two contact sets unconnected. Code bars CG1, CG2 are selectively displaced to admit an interponent to an appropriate one of the columns 14 to 17, while code bars C1 C2, C4, C8 are selectively displaced to admit an interponent to an appropriate one of the columns 1 to 13. Energization of a bridge magnet (not shown), will operate the chosen columns of contact springs which are held operated by the spring force of the operating armature after the bridge magnet is released. One set of springs is therefore released only when another set is operated. The normal condition of the switch is with columns 13 and 14 operated so that a disconnected contact set is involved. In the normal condition each bridge may have contacts HV which are broken only in this condition. Should the bridge inlets employ a fourth wire d as well as a, b and c, the rows are arranged in three groups of four for triple instead of quadruple group working, as is the case with the stage SLB. The selectors are of the kind described in Specification 832,865. Detailed description.-A call from a satellite subscriber is described with connections made as far as an originating relay set SNR and a call to a satellite subscriber is described assuming the connection has already been established to an inlet of stage SLC. Call from satellite subscriber.-In the identifier SIDS, Fig. 4, the sixteen relays SA65 to SA80 mark the particular row of the particular selector SSLA to which a subscriber is connected while the relays SB1 to SB13 mark the column containing the connection. If subscriber 800 is off-hook SA65 operates to join SBA which is normally operated. Relays SAA and SI65 follow SA65 to operate SB1 which disconnects higher order SB relays so that in the event of simultaneous calls only one SB relay responds. With SB1 operated SBA releases and energizes SBB which marks wire 2 of the wires 1 to 20 to the main exchange, wire 2 going to Fig. 6, where it becomes wire 14 and goes to the main exchange identifier MIDS to operate relay MAU in Fig. 5. In MIDS relay MAA operates and joins MBA which is normally operated. In this condition the main exchange returns a mark over wire 35 which becomes wire 11 in Fig. 6 to operate relay SAN in the satellite thereby acknowledging the initiation of a call. Relay SAN connects potential to the code wires 3 to 6 marked by the relay SB1 so that in the satellite supervisory circuit of Fig. 6 corresponding ones of the relays MD1 to MD4 respond. In the particular case of subscriber 800 all four wires are marked and all four relays respond, bringing up relay MDA and marking the wire 1 of wires 1 to 13 from Fig. 6 to Fig. 5 so that relay MB1 responds in identifier MIDS. Similarly, the relay SAN connects potential to code wires 7 to 10 marked by relay SA65 to operate the four relays ME1 to ME4 so that wire 19 of wires 19 to 34 is marked and relay MA65 operates in identifier MIDS. Operation of the MA relay acknowledges receipt of the calling satellite subscriber's identity by returning battery on wire 37 through Fig. 6 to wire 1 which at the satellite operates SW, thereby receiving a mark on wire 12 to operate MDEA in the main exchange, Fig. 6. When MB responded, MBA was released and MBB operated to energize MVMA which connects the code wire 5 to the code-bar magnets MCG1, MCG2 &c., of selector MSLA17 and also connects a test path to each of the bridge magnets MVO to MV9 of this selector. If a magnet is associated with a busy bridge the d-wire is marked with positive potential from a relay set and the associated one of the test relays IT0 to IT9 cannot operate. If the d-wire is disconnected the test relay is energized. Since the call involves an originating relay set SNR an idle path has to be found from MSLA17 to one of the selectors SLB1 to SLB5 and this is indicated in the identifier MIDS, Fig. 5, by relay MRN which is not operated and puts battery on wire 4 which over contacts of FB in the marker SLM, Fig. 7, and contacts of the operated test relays ITO to IT9 energize relays VMB1 to VMB5 of selectors SLB1 to SLB5 and leave relays VMB6 to VMB10 disconnected. Each one of the relays VMB1 to VMB5 may be operated by either one of an associated pair of test relays which corresponds to the connection of two MSLA17 bridges to each SLB selector. The relays VMB1 to VMB5 connect up the bridge and code magnets of their associated selector the idle bridges of which are marked from relay sets SNR over back contacts of relays S1 and S8. The ten such marking wires from each set of ten SLB inlets go to an associated one of the relays F1 to F5, the lowest numbered of which operates and disconnects the rest to choose the lowest numbered SLB selector with a free inlet. With an F relay operated the ten marking wires from the chosen SLB selector are connected to the relays G0 to G9 the lowest numbered of which operates to disconnect the rest and thereby choose the lowest numbered free bridge. The operated F relay also releases the normallyoperated relay FA which connects up FB and thereby releases all but the wanted one of the relays VMB1 to VMB5 so that only the code and bridge magnets of the wanted SLB selector are connected. Since two bridges, say those with magnets MV0 and MVJ may be idle ir selector MSLA17 and have access to a free inlet of selector SLB1 with VMB1 operated, it is necessary to select one of these bridges and this is done with secondary test relays 2T0 to 2T9 arranged in pairs. In this instance, with F1 operated and test relay 1TO indicating MVO idle, secondary test relay 2T0 operates and identifies the appropriate outlet of SLB1 by operating relay TJ and not TU to select one of the two possible codes derived from MA65 in identifier MIDS and connected to the code magnets of selector SLB1. Since bridge magnet MVO has been chosen in the main exchange in selector MSLA17, bridge SVO must be chosen in the selector SSLA17 at the satellite and this is done over contacts of secondary test relay 2T0 marking all wires 21 to 24, which overcontacts of MDEA in the supervisory circuit of Fig. 6 become wires 13 to 16, to operate relays ST1 to ST4 in the satellite. Relay STA follows the relays ST1 to ST4 and operates the appropriate combination of code magnets according to the state of identifier SIDS. In the assumed case of subscriber 800 calling, only code-bar magnet SC1 is operated. The appropriate code-bar magnets in the stages MSLA17 and SLB1 at the main exchange are operated, according to the state of identifier MIDS, by relay GA in the marker SLM of Fig. 7, which energizes when the relay chain G0 to G9 is taken into use. The magnet SVO at the satellite is operated by relay SVK1 which follows STA and pulses the magnet for as long as SVK2 takes to operate. In the main exchange br