Patent GB-698328-A (GB)
Title: Automatic telephone system comprising cross-bar switches and markers
IPC: H04Q3/00
Filed: 1950-05-04
Abstract: 698,328. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. May 4, 1950 [May 6, 1949], No. 11059/50. Class 40 (iv). Selectors comprising primary and secondary cross-bar switches are controlled by registers and markers and are guarded against the simultaneous connection of several markers by means of a chain of marker connecting relays in each selector. The marker selects a route through the switches and employs relay chains to select one of a number of free links. Links between selectors are collected into groups which are tested successively as claimed in Specification 698,177. An alarm is given if no free route is available. General arrangement. Figs. 3, 4 should be arranged beneath Figs. 1, 2 to show details of two selectors A, D and of a marker M in the arrangement shown in Fig. 5. A calling line is connected through switch RS to a register REG which operates a switch MS to seize a marker, Figs. 3, 4. When the called number is registered, a relay R9 (in a group R7-R9) and a relay R12 (in a group R10-R12) operate to mark the incoming and outgoing selectors A (K1-K4) and D (K5-K8) in which the calling and the wanted lines appear. The wanted line or group of lines is marked by operation of relays V3, V4 controlled by a registering device MR in the marker. The calling line is marked later over wire d from line circuit LR. When marking relays R9, R12 operate, connect relays M12, M22 operate in series and relays M11, M21, R6 follow. Relay R6, at contact 164, starts an operation to select a route through the switches. Relays M12, M22, relays M13, M23 and relays M14, M24 are controlled by different markers. Selection of a route. Select magnet S11 is operated from contact 162 in the marker and is followed by relay K11 which connects the test wires of the switch links available to the marker primary switch K1 to a chain of test relays which are connected to negative battery by relay R41. Test potential (ground on contact 99) is connected through switch relays P20-P21 to the test wires of all the lines T1-T4 marked by V3, V4. The test circuits are normally open at contacts of relays V1-V2. When relay R6 operates, however, relays R1-R5 interact to operate relays V1-V2 to complete, in sequence, the test circuits of groups of links between selectors. If, when V1 operates, it completes the test circuits of one or more links through which the desired connection may be made, one of the test relays, say R20, operates in series with the low and high resistor on windings I, II of a switch relay, say P20, relay R41 falls back and the sequential operation of V1-V2 ceases. More than one switch K7-K8 may have access to the same links controlled by V1 but relays P20-P21 are arranged in a chain so that only one can operate. Relay P20 connects a chain of relays R30-R39 which select but do not operate an operating magnet, say B81, for the first free line. T1 of the marked group, available to the secondary switch K8. Relay R40 falls back and operating magnets B11, B42, B51, B81 are operated over contact 401 and wires m, t, v. In the meantime select magnets S41, S50, S81 are operated in the test circuit when relay P20 is held through its low resistance winding I. The register and the marker are released and the operating magnets are held over their own contacts. An alarm AL is operated if no route is found.