Patent GB-890235-A (GB)
IPC: H04Q3/00
Abstract: 890,235. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. April 27, 1960 [May 9, 1959], No. 15974/59. Class 40 (4). An exchange has groups of subscribers, each group being served by a set of primary and secondary switches giving access to call originating trunks and being accessible to call terminating trunks, the originating and terminating trunks being connectible over the or one of one or more switching sections, each of which comprises primary and secondary switches and is divided into two sub-sections by linking the outlets of the primary switches to one or other of two groups of secondary switches, each group of secondary switches having access to all subscribers, so that two calls may be set up at the same time, one over each of the subsections of a switching section, unless the calls are to the same group of subscribers. Switches.-As shown in Fig. 1, the cross-bar switches used in the exchange have ten bridge magnets BK1 to BR 10 and twelve select magnets connected for triple-group working. Each of the nine select magnets 1SM to 9SM controls corresponding cross-points multipled across the bridges while three auxiliary select magnets 1AM, 2AM, 3AM, determine which of three possible outlets at each crosspoint is to be connected to an inlet when one of the bridge magnets BR1 to BR10 is operated. Once the spring sets chosen by an auxiliary select magnet and a select magnet have been operated by a bridge magnet the auxiliary select, and select magnets are released. The select magnets are arranged in pairs to pivot, left or right, a common select bar. Select magnet 9SM and auxiliary select magnet control the same select bar and cannot be energized at the same time. This bars an outlet in the cross-points controlled by 9SM and reduces the outlets to 26. Each crosspoint comprises contacts for, at least, A, B and P wires. It is said although no such arrangement is employed in the exchange described, that each inlet can give access to a different group of 26 outlets if the outlets are not multipled across the bridges. General description of 10,000 line exchange. Figs. 2 to 5. Subscribers divisions.-Subscribers' lines SL are connected over frames MDF, LIDF to line circuits SLC and are grouped in 20 divisions of 500 lines each. Each division, as shown with DIV. 1 in Fig. 5, is served by 20 primary line selectors LS/PRI and 8 secondary line selectors LS/SEC. In groups of 25 the lines of a division are connected to the outlets of the switches LS/PRI, one of the possible outlets being ignored in each switch. The ten inlets of each switch LS/PRI are distributed over links LKS to give access from all switches LS/SEC. - Inlets 1 to 5 of switches LS/SEC serve 40 terminating trunks TT1 to TT40, while inlets 6 to 10 serve originating trunks OT1 to OT40 which, together with similar groups of originating trunks from the other 19 divisions, have access over distribution frame TDF, Fig. 2, to 6 trunk sections of which SECT 1 is shown in Figs. 2 and 3. In each division a start shift circuit SSC controls testing of trunks in successive groups of five and ensures that each successive testing cycle is started one group ahead of the last cycle to equalize the use of the secondary switches. Furthermore, each division has 6 pairs of entry relays sets, such as ERS1A, ERS1B, which control access to the divisional marker MKR from the 6 sections SECT 1 to SECT 6. The trunk sections, Figs. 2 and 3.-Each of the sections SECT 1 to SECT 6 is accessible from and gives access to all of the 20 divisions. Each section receives 160 incoming trunks terminated on trunk relay sets TRS1 to TRS160. As well as the 800 originating trunks from divisions the sections also receive, or if required a single section may separately receive, trunks AA, MAN, and TR, from automatic, manual, and trunk exchanges, incoming on junctions IJ, and trunks TD from a test desk. Each section has a first stage of 16 switches IS1 to IS16, each serving 10 relay sets TRS. In this stage only 25 outlets are used in each switch pairs of which are connected in multiple with the outlets divided into sub-sections A and B, half the pairs of switches having 12A and 13B outlets and the other half having 13A and 12B outlets. The A outlets give access to all of 10 second stage A switches 2SA1 to 2SA10 over links ALKS. The B outlets give access to all of 10 second stage B switches 2SB1 to 2SB10 over links BLKS. Second stage switches put to use all 26 outlets, 20 trunks LOA from each A switch and 20 trunks LOB from each B switch giving access in groups of ten to divisions 1 to 20 over a strapping field SFA which also receives similar groups of trunks from the other sections. The remaining 6 outlets from each of the second stage A and B switches form groups of outgoing trunks JOA, JOB, connected to outgoing junctions OJ. First choice registers 1BEG1 to 1REG16 are provided, one to the relay sets of each first stage selector; second choice registers 2REG1 to 2REG4 being available to sets of four first stage selectors. Allotters RA1 to RA10 control access to the registers. When a trunk relay set TRS has been seized and associated with a register, section marking control circuits SMCA and SMCB are consulted for permission to proceed. Permission to proceed given by SMCA causes the associated allotter RA to effect discrimination in the first stage selector so that a path may be set up only over the subsection A outlets to the A second stage switches. Permission to proceed given by SMCB similarly restricts the path to sub-section B outlets to the B second stage switches. By this means the sub-sections A and B may be used simultaneously to set up two paths over a section. To mark a wanted subscriber in a division multi-conductor digit transfer paths TPA, TPB used for sub-section A and sub-section B paths, respectively, are provided in common to all registers of a section and are terminated in multiple on marker entry relay sets, such as ERS1A, ERS1B, in all divisions. To discriminate the wanted division the entry relay sets are controlled by individual leads DA, DB from each section. Outgoing junctions.-Each section is provided with junction route discriminators JRDA, JRDB, available to all registers in the section, which seize an idle trunk from the groups JOA or JOB depending on whether section marker SMCA or SMCB is active. The trunks are extended beyond the section to outgoing junction relay sets OJRS-1A, OJRS-1B, by marking relays such as IJMA, IJMB. For outgoing calls the registers of a section have access over the distribution frame TDF to local senders LS, national senders NS, and tariff computers TC. Originating trunks.-The 40 trunks from each division to the distribution frame TDF are spread over the sections in 4 groups of 7 and 2 groups of 6, the trunks of a group to a section being spread as evenly as possible over first and second choice registers. Terminating trunks.-Each section contributes 10 trunks LOA and 10 trunks LOB to each division by way of strapping fields SFB, SFA. Each division thus receives 120 trunks which are concentrated three to a termination TT1 to TT40. The terminating trunks LOA or LOB from a particular section can be marked to the inlets of the secondary line selectors LS/SEC of a division by marking relays such as ITTMA, or ITTMB, each of ten contacts, controlled from the entry relay sets of the section in concert with the divisional marker. Exchange subscriber originates call.-A line relay responds to a calling loop and a discriminating relay operates in the relevant primary line selector LS/PRI to indicate an originating call and mark the ten links terminated on the switch. Each link has a discriminating wire and a marking wire as well as A, B and P wires. The select magnets appropriate to the calling line and select magnets corresponding to idle links LKS operate in the primary and secondary line selectors. Start shift circuit SSC tests the 40 originating trunks of LS/SEC in successive groups of 5 from a preallotted point which is advanced by one group for successive calls. Test relays in the selectors LS/SEC identify trunks with access to free relay sets TRS associated with free registers. Testing advances until an idle trunk is found or all 8 groups are testing. If an idle first choice register is available testing halts when it is found and the bridge magnets between the idle trunk and the calling subscriber are operated. An idle second choice register is detected by a delayed relay which only agrees to its connection when it is clear that no first choice register is free. The chosen register tests for continuity of the line and records the class of service to be afforded by detecting a characteristic potential on the line. The cutoff relay responds, select magnets over the path are released, dial tone is connected from the seized transmission relay set, and the register waits for impulses. Local exchange call.-Given enough digits the register consults SMCA, SMCB and if both are busy waits until one becomes idle. Arbitrarily, SMCA or SMCB gives permission to mark the wanted subscriber's line. Supposing that transmission relay set TKS10 and register 1KEG1 have been seized in section SECT 1 and SMCA grants permission to proceed, then TRS10 is terminated and its associated first stage selector 1S1 is conditioned to be responsive to backward marking only over links ALKS and the second stage selectors 2SA1 to 2SA10. If the call is to division DIV 1, potential is put on conductor 1DA to put entry relay set ERS1A into use and seize marker MKR in DIV 1. Terminating trunk marking relay 1TTMA operates to connect the M-wires of the ten trunks LOA from SECT 1 to the terminations TT1 to TT40 in DIV 1. The multi-digit transfer path TPA is extended over ERS1A to MKR and marks hundreds, tens, and units leads to extend the -mark to the wanted subscriber's line circuit. If the line is busy SMCA responds to