Patent GB-414106-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1933-01-26
Abstract: 414,106. Automatic exchange system. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, TAYLOR, R., 30, Oulton Road, Wavertree, both in Liverpool, and MASON, J. A., 52, Belgrave Street, Liscard, Wallasey, Cheshire. Jan. 26, 1933, Nos. 2560 and 16998. [Class 40 (iv).] In an alternative routing system, a single impulse-sender (dial or register-controller) transmits the whole of the impulses required for setting up a connection over an indirect route which is taken only after a search over all the direct routes, the fate of the impulses (suppression or route) being determined by the switches used in setting up the connection so that this proceeds uninterruptedly without the re-setting of switches, delay in impulse sending or auxiliary impulse senders. In a rural system, calls from one rural exchange to another may proceed directly over a group selector which causes the second digit to be suppressed, or indirectly over a main exchange junction seized by a hunting switch associated with the group selector, the second digit being used to set the incoming selector. The hunting of the group selector and junction switch may occur substantially simultaneously. When bi-directional switches are used the junction switch is dispensed with and direct and indirect junctions appear in the same level, the indirect junction appearances being obtained by multiple connections to another level reserved for direct main exchange calls. As applied to satellite systems, the first or first two digits simultaneously set group selectors at the satellite and main exchange in the usual way. If the call is to an adjacent satellite, it may proceed directly, the main junction being released, or if all direct junctions are busy, the main junction is maintained in use and the call is set up over the main exchange switches. The invention is described with reference to lay-out diagrams only. When a register-controller is used, the control may be by direct or revertive impulsing or by marking. Rural systems, Fig. 1 and Fig. 2 (not shown). According to Fig. 1, a 50-line rural exchange comprises single-motion finder-connector links LF, S1, the connector S1 also having access to two-way junctions BWR to an adjacent rural exchange. Access to a main exchange is obtained over two-way junctions BWM an idle one of which is seized over a hunting switch JH, the main exchange also forming an alternative route to the adjacent rural exchange. The two-way junctions BWM, BWR appear in the banks of the finders LF, incoming calls being treated in the same way as local calls. For a call to the main exchange (first digit 0), the connector is set to a characteristic position and, as a result, the junction switch hunts for a junction. For a call to an adjacent rural exchange (initial digits 99), the connector hunts for a direct junction, e.g. under control of a marker, and if an idle one is found, the second digit 9 is absorbed. The switch JH starts to hunt for an indirect junction either when the call is initiated, or after receipt of the first digit, or after an unsuccessful search by S1, and if S is unsuccessful, an incoming selector at the main exchange is controlled by the second digit 9 to select a junction to the adjacent rural exchange. The number of direct junctions to the adjacent rural is about half that required for all the traffic. In a modified arrangement, Fig. 2 (not shown), using 200-point bi-directional finders and connectors, the connectors are caused by post springs on the 9th level, to hunt for a direct junction, the second digit 9 being absorbed if one is found. If not, 11th step springs make a circuit for starting up the junction switch, and the second digit 9 is sent to an incoming selector at the main exchange. Modified rural system, Fig. 3. This system comprises two ranks of selectors SI, FS, the main exchange junctions appearing in the O level of the group selectors while the adjacent rural exchange is reached by dialling 99 as before. The main exchange junctions comprise one-way junctions OGM and two-way junctions BWM. The first choice outlets (say two) in level 9 of S1 comprise one-way and twoway direct junctions BWR, OGR to the adjacent rural exchange, the remaining outlets being graded with the main exchange outlets in level 0. If S1 finds a direct junction in level 9, the second digit 9 is absorbed, if not, the switch proceeds to hunt in the same level for a junction to the main exchange at which the second digit 9 is used to reach the adjacent rural exchange. For incoming calls from the main exchange over one-way junctions ICM and the both-way junctions BWM, group selectors SM are taken into use, while for similar calls over ICR, BWR from the rural exchange, group selectors SR are used. Overflow finders are connected to group selectors over secondary finders SCF as described in Specification 366,143. Alternative routing in satellite systems. As shown in Fig. 4, a satellite A may reach an adjacent satellite B directly or over main exchange T. When any call is made, the switch JH seizes an idle junction to T and group selectors S1, S2 at A and T are set by the first digit as usual, and if the call is to B both switches hunt for an idle junction thereto. If the satellite selector S1 is successful, the junction to T is released and the second digit passes to B over the direct junction. If not, S1 proceeds to last contacts, the junction to T is maintained and the second digit passes to B over the indirect route. The usual release of the junction in case of local calls may be deferred until hunting for a local trunk has taken place. In a modified system, Fig. 5 (not shown), the direct junctions to B and the junctions from T to B appear in the second group selectors of the respective exchanges, and corresponding switches in A and T are operated simultaneously by the first two digits. In the further modification shown in Fig. 6, satellite A has direct access to two small exchanges B, C over the 5th and 3rd levels respectively of S1, alternative routes being provided over JH and junctions to the main exchange T at which an incoming selector S2 obtains access to junctions to B and C over levels corresponding to those of S1. If the call is local (first digit 4) S1 drops back and takes the second digit (6-9), the main junction being released. It may be arranged that the release of the junction is deferred and if all the second group selectors are busy, the connection may be completed over S2 at T and a junction back from T to A. Discrimination may be effected by the group selectors or by common apparatus available to a group of selectors. The above-mentioned overflow-finder arrangements may be applied to the system shown in Fig. 6.