Patent GB-930318-A (GB)
Title: Improvements in or relating to circuit arrangements for restoring selector relays inan automatic telephone system employing relay selectors
IPC: H01H67/32
Filed: 1960-03-25
Abstract: 930,318. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. March 25, 1960 [March 26, 1959 (2)1, No. 10725/60. Class 40 (4). In a telephone system using relays with selectively operable sets of contacts, otherwise called bridges, the construction of the bridges is such that they are always held operated even though a talking path over them has been relinquished and they are unoperated only while a bridge magnet is pulsed to transfer the bridge from one selected connection to another, a home condition of each bridge being indicated by an operated state the corresponding outlet to which is sacrificed to permit the operation of home position contacts thereby providing test paths enabling a marker to detect off-normal bridges which are no longer in use and need to be restored to home position. Construction of bridge.-As shown in Fig. 1, a bridge has vertical sets of contacts 1 operated by lift bars 3 to make contact with wires 2. To each lift bar 3 there is an interponent 4 pivoted through a vertical slot 14 on a bar 13 and having a feeler arm 7 to sense for a slot produced by coincident positioning of a set of slotted code bars 8. Where a feeler finds no slot across the code bars 8 it is tilted so that its heel 11 lies clear of a lifting armature 5 which is normally held up by a spring 12. If a feeler finds a slot it is pressed downwards into the slot by a spring 10 so that when the bridge magnet 6 is pulsed the armature 5 is pulled down and allows the interponent to pivot and place its heel over the operating edge of the armature. When the magnet releases, the armature spring 12 lifts the interponent and its associated contact bar 3, the interponent rising to the extent of its slot connection on the rod 13 and thereby raising its feeler 7 clear of the slot across the code bars. As shown in Fig. 2 a bridge comprises 17 columns of twelve contacts. Each contact shown represents a group of three contacts for a three-wire line. The inlet to the switch is connected in common to contacts in the last four columns 14 to 17 each of which columns connects the inlet to one of the four rows of contacts into which the outlets are arranged and selection of which is made by two code bars CG1, CG2. Code bars C1, C2, C4, C8 select a particular one of the columns 1 to 13 in which the bridge outlets are arranged. Black spaces on the code bars indicate slots in the bars which occupy either the rest positions shown or are displaced to the left by associated magnets. Wide gaps left in the . bars CG1, CG2 prevent them interfering with selection made by energization of a combination of the magnets of code bars Cl, C2, C4, C8 and vice versa. In the home position of the switch with no code bars displaced the columns 13 and 14 are operated and the outlet in the bottom row which is connected to the inlet is unwired and the normally operated lift bars for columns 13 and 14 hold up a pair of normal contacts H to connect marking to an idle wire h. When a different pair of lift bars are chosen the marking is extended to an off-normal wire u. The two contacts H may be replaced by a single contact which can be operated by both lift bars but not one alone. In the exchange shown in Figs. 6, 7, 8, 11 and 12, these contacts are shown as single contacts HK. If four-wire lines are to be switched over a bridge only three rows of outlets are possible and the code bars are as shown in Fig. 3. With twelve-wire lines the bridge reduces to one row as shown in Fig. 4. To provide a selector ten bridges are used with a common set of code bars. General description of exchange.-The exchange in which the bridges are used is shown schematically in Fig. 5. A calling subscriber is connected to line identification circuit IDS and a marker SLM which connects the subscriber over idle selectors SLA, SLB, to a link circuit relay set SNR from which an idle register REG is seized by means of a marker RSM and a finder RS. The register stores dialling impulses and seizes an identifier IDG which over group selector GVA connects the relay set to a code receiver GKM and instructs marker GVM to extend the connection over group selector GVB. From here an identifier IDC connects code receiver KMS to the register and passes instructions to marker SLM to set up a path to the wanted subscriber over selector stages SLA, SLB, and SLC and an incoming line circuit LKR. Detailed description. Connection to relay set.- Figs. 6, 7 and 8 show the selector stages SLA, SLB, the marker SLM, link circuits SNR, five registers REG, the finder RS and the marker RSM. The selector stage SLA comprises 20 selectors each comprising ten bridges of the kind shown in Fig. 2. Each bridge has one inlet and 20 outlets so that a selector has 10 inlets and 500 outlets. The 20 selectors SLA allow 1000 subscribers to be connected over 200 three-wire lines to selectors SLB. The identifier IDS comprises a matrix of line relay contacts in 13 columns associated with 13 B relays and in 80 rows associated with 80 A relays. Subscribers' lines associated with one selector SLA are to be found in four adjacent rows of the identifier corresponding to the rows they are to be found in the selector. A calling subscriber puts positive potential on to his contact in the identifier where an A, followed by a B, relay operates. The B relay responds to operation of one of the auxiliary relays A101 to A180 and releases a normally energized relay BA which allows BB to respond. The operated A relay marks the appropriate ones of the code-bar magnets C1, C2, C4, C8 of the selector to which the A relay relates and brings up the associated one of 20 connecting relays VMA which connects up the home position contacts HK over bridge magnets V0 to V9 to the marker SLM, Fig. 7. Relays IT0 to IT9 test the condition of test wires comprising a fourth wire to the selectors SLB. Idle bridges are marked over these wires by their lack of connection while occupied bridges have these wires marked with positive potential from the relay set SNR employed with the call. Negative resistance battery over M0 to M9 operates test relays IT0 to IT9 for those bridges found idle and operation of one or both of the pairs IT0, IT1 or IT2, IT3 to IT8, IT9, energizes a relay VMB1 to VMB5 respectively. Trunking between selectors SLA and SLB is shown in Fig. 9 where a group of 50 subscribers is connected in multiple to the ten bridges T0 T9 of each of the 20 SLA selectors. The SLB selectors have 40 inlets to each bridge and ten bridges to each selector with bridges as shown in Fig. 3 where each contact represents a 4- wire contact set. The outlets from the first two bridges in each SLA selector are connected to the 40 multipled inlets of an SLB selector, shown as F1; the outlets of the second two bridges in each SLA selector going to F2, and so on to F5. Operation of one or more of the relays VMB1 to VMB5 connects the bridge and code bar magnets of the idle SLB selectors. Each bridge in an SLB selector has a relay set SNR which, if a register is free, is marked idle over the wire f, from Fig. 8 to Fig. 7. Each of the ten such f wires from relay sets of a particular SLB selector is connected in a column of contacts in the identifier matrix with a column relay chain Fl to F5 and a row relay chain GO to G9. In this identifier an F relay energizes releasing a normally operated relay FA allowing FB to respond so that a G relay responds to mark an idle bridge in selector SLB and relay set SNR. Depending on which selector SLB is W involved the F relay operates one of the relays in one of the pairs 2T0, 2T1, or 2T2, 2T3, to 2T8, 2T9 so as to select one relay from the pair IT0, IT1, or IT2, IT3, &c., associated with the seized selector SLB. A relay TU or TJ responds according to which one of the test relay pairs is chosen, and extends the code marking from the identifier IDS to the code bar magnets C1, C2, C4, C8 of the SLB selector. The operated relay G marks the wanted bridge magnet in the selector. Relays GA and GB respond in the relay set identifier and connect operating potential to the code bar magnets of both selectors SLA and SLB over the wire f from Fig. 7 to Fig. 6. Operation of relay US follows to pulse the selected bridge magnets, US being released by K2, which it operates, K2 also disconnected the code bar magnets and connects up K3 to energize the relay HS which restores idle but off-normal bridges in the SLA selector. A contact of HS puts positive potential over the U-wire of all off-normal home-position contacts HK which pulses their bridge magnets V0 to V9 to restore them, and change the HK contacts to the H-wire, in a circuit back to negative potential on an HS contact including operated and unoperated test relay contacts of the pairs such as ITO, 2TO, respectively. The bridge magnet of SLA just used to set up a connection is not affected by HS as its associated relay, such as 2TO, is operated. Thus, according to the invention, bridges used in an old call and relinquished are restored each time the selector is taken into use for a new call. Connection of register.-At the same time as connection is made over selectors SLA, SLB, a register is connected over selector RS. Selector RS uses bridges of the kind shown in Fig. 4 where the contacts represent 12-wire lines and each bridge has 15 inlets. As shown by the trunking diagram of Fig. 10 RS comprises two selectors RS1, RS2, each having ten bridges which may be considered to occupy two rows of five each. Each set of ten bridges has a set of code bars C1 to C32, see also Fig. 8. Corresponding columns of RS 1 and RS2 show bridge outlets connected in common to registers REG1 to REGS. The four rows of the two selectors give a possible 60 inlets of which only 50 are used to connect with the outgoing sides of the 50 relay sets SNR. The relay set seized for the call in association with a free register is marked by the operated G relay in the relay set identifier, Fig. 7, and e