Patent GB-204118-A (GB)
Abstract: 204,118. Aitken, W. June 21, 1922. Automatic and semi-automatic exchange systems.-In a relay switch of the kind described in Specification 181,134, in which one or a combination of two connecting relays are energized to extend a calling line to an idle outgoing line of a group, control relays associated with the outgoing lines energize as the latter are taken into use and prepare the circuits of the connecting relay or relays which will extend connection to the next idle line immediately their circuits are completed over a single contact of the line relay of the calling line. The application of such relay switches to line switches and group selectors is described as applied to a system in which the trunk or junction lines are multipled over the relays of small capacity switches which preselect the outgoing lines in a definite order. Large groups of incoming lines, say 1000-line groups, are subdivided into 20 smaller groups of 50 lines and a group say of 59 outgoing trunks is subdivided unequally and multipled in the preselector groups in the following manner. Twenty trunks are allotted as first choice lines each trunk being multipled in all the switches of one subgroup, ten trunks are allotted as second choice lines each being multipled in the switches of two subgroups separated by another subgroup, ten trunks are allotted as third choice lines each multipled in two subgroups separated by three other subgroups, ten trunks are allotted as fourth choice lines each multipled in two subgroups separated by nine other subgroups, five trunks are allotted as fifth choice lines each multipled in four subgroups separated from one another by four other subgroups, and four trunks are allotted as sixth choice lines each multipled in five subgroups separated from one another by three other subgroups. The above figures are only given by way of example, and the repetitions of the multiple in the subgroups and the number of trunks allotted to each choice may be varied to meet particular traffic requirements. In the 10,000-line exchange system described, an idle trunk to the wanted section of the exchange is preselected at every connecting stage by a relay switch. Incoming subscribers' lines each of which terminates in a 6-point preselector, are divided into 1000-line groups A, B, Fig. 1, which are subdivided into 50-line groups. A group of trunks leading to first group selectors is allotted to each 1000-line subscribers' group and multipled in the subgroups thereof according to the above-described method of proportional multipling. For example, 59 trunks are allotted to the group A, trunks 1, 21, 31, 41, 56 being multipled in all the preselectors of the first subgroup 0-49 in the choice order named, trunks 2, 22, 32, &c. are multipled in the switches of the second subgroup 50-99, and so on. These trunks terminate in 60-point first group selectors and are divided into twenty groups, each group including trunks from each 1000-line subscribers' group, the first group for example comprising trunks 1, 21, 41 from group A, trunks 1<1>, 21<1>, 51<1> from group B, and trunks (not shown) from each of the other groups. Each first group selector has access to six trunks to each thousands division of the exchange the trunks to which are proportionally multipled in the selector groups in a manner generally similar to the preselector multipling, the distribution of 59 trunks to the finst thousands division, and 51 trunks to the last thousands division being shown in Fig. 1. When a trunk to a first group selector is taken into use a relay group I<c> selects an idle marking switch I<r> which in response to the first digit marks the wanted thousands group in the selector and the connection as extended to a second group selector over a preselected idle trunk. The trunks to each thousands division are divided into groups and the trunks to the hundreds division are multipled in the second group selectors in a manner similar to that described with reference to the first group selectors. The second group selectors have access to five lines in each hundreds division. The grouping of the incoming trunks in the first thousands division, and the multipling of 23 trunks to the first hundreds division and 10 trunks to the last hundreds division are shown. The second group selectors extend connection to a preselected trunk in a wanted hundreds division marked by a marking switch I<r>. Each outgoing trunk from the second group selectors terminates in a distributing switch in which are multipled two sets of 50-point connectors serving the two halves of the hundreds section of the exchange to which the trunk leads. An idle twoco-ordinate marking switch selected over the engaged trunk is set by the last two digits the completion of tens and units marking circuits causing the call to be routed over the distributing switch to a preselected idle connector serving the wanted half-section, and operating the seized connector to pick out the wanted line. Preliminary selector. Fig. 4 shows a preselector individual to the first group 0-49, having access to six trunks 1, 21, 31, 41, 51, 56, the calling line being extended to an idle one of these trunks by the energization of one of the relays a, b alone, or one of the relays a, b together with one of the relays m, n. Each trunk has associated with it a controlling relay TC1, TC21 &c. which is energized when a trunk is taken into use and remains energized during the connection. Four common conductors multipled to the bottom points of the energizing windings of the relays a, b, m, n of all the preselectors of the subgroups in question, are adapted to be selectively earthed over the contacts of the relays TC1, TC21, &c. in such a manner that the circuit or circuits of the relay or pair of relays, which will extend connection to the next idle trunk, is prepared in all the switches by the energizatoin of the controlling relays TC1, TC21, &c. of the trunks already in use. Fig. 8 shows the manner in which the contacts of the trunk control relays TC1, TC21, &c. are connected where a trunk is multipled in two or more subgroups. When such a trunk is an intermediate line of access, such as 21, the trunk controlling relay operates spring groups C21 in each of the subgroups 0-49 and 100-149 in which the repetition of the multiple occurs, or controls separate relays in these subgroups for this purpose, but where the trunk is a final line of access, such as 56, the multiples of the subgroups are carried to a common spring group C56. The trunk guard relays may conveniently be used as trunk-controlling relays. Assuming that none of the trunks are engaged, on the response of the line relay R1, Fig. 4, a circuit 2 is completed for the relay a which extends the calling line over the first outgoing trunk 1 to the line relay R3 of a repeater BF. The response of a slow-release relay R4 completes a circuit 6 for the trunk-controlling a relay TC1 which prepares the circuit of the relays b of all the other preselectors in the subgroup. The relay a locks up over its upper winding and a third conductor in a circuit 5 in which the cut-off relay R5 is also energized. An alarm-signal circuit s may be completed and a meter operated each time the last trunk of a switch is taken into use. Selection and setting of an idle marking switch Ir'. The line relay R3 also closes a circuit 7 for a relay IF' which locks up in series with a guard relay R8 and extends the impulse circuit to the stepping magnet M9 of the first marking switch I<r1> which it is assumed is idle. The relay R8 prepares a circuit 10 for the relay IF2 which on another call coming in takes into use the next marking switch I<r2>. On the transmission of the thousands digit an impulse circuit 9 is intermittingly completed for the stepping magnet M9 which steps round the marking switch. The slowrelease series relay R9, which throughout the impulses holds a slow relay R11 energized, relapses on their cessation and earths the selected marking wire. A moment later the relay R11 falls away and completes a circuit 12 for the release magnet R<e1> which restores the switch in known manner, opening the holding circuit 8 of the relays R8, IF<1> and rendering the marking switch available for another call. When the last marking switch is taken into use a circuit is completed over conductors s for a signal or meter. A slightly modified form of marking switch is described in which the starting circuit is not extended to the next marking switch until the subscriber begins dialling, so that if he delays dialling a second subscriber can take into use this marking switch and connect the first subscriber to the next switch. If it is desired that a large group of incoming trunks shall have access to a large group of marking switches, the incoming trunks are divided into subgroups and the marking switches are proportionally multipled to the marking switch selecting relays of the subgroups in a manner similar to the multipling in the general trunking scheme. First group selector. The completion of a marking wire circuit causes the seized group selector to extend the connection over a preselected idle trunk to the wanted thousands section of the exchange in the manner described in the next paragraph with reference to the second group selector. Second group selector. On a trunk to the wanted thousands section being taken into use, a marking switch is selected and set by the hundreds digit to mark a hundreds wire, in the same manner as described with reference to the marking switch Ir<1> in the previous trunking stage. The group selectors are similar in general arrangement to the preselectors, a group of trunks to the wanted section of the exchange being selected by the energization of one of the relays a - - k, Fig. 2, and an idle trunk in the selected group being selected by the energization of one of the relays m - - q. The spring groups C1, C