GB885609A - A contact field arrangement in an automatic telephone or telegraph exchange - Google Patents

Abstract

885,609. Automatic exchange systems. TESLA, NARODNI PODNIK. Oct. 30, 1959, No. 36907/59. Class 40 (4). In a two - stage cross - bar switching system incoming lines are fed to the first stage over a split and staggered multiple. As shown in Fig. 2, 100 incoming lines 00 . . . 99 are given access to 30 inter-stage links 1 . . . 30 (leading to a second stage switch) over three cross-bar switches I, II, III assembled effectively as one large switch. It is seen that a pair of incoming lines, say 02, 12 have access to links 3 . . . 8 whereas lines 03, 13 have access to links 4 . . . 9 and so on. The arrangement gives flexibility without giving up the advantages of bare-wire multipling. Chain arrangements, Fig. 3, are described for selecting a link when an incoming line is marked (either calling or called). The marking, say of line 03, involves the operation of a horizontal magnet 3H A and the operation of a D relay (say 1D) indicative of a group of twenty lines. The D relays are chain connected so that only one can operate at a time. The H A magnets are similarly connected. It will be noted that the two 3ha contacts isolate a portion of the chain corresponding to links 4 . . . 9 and with 1D operated circuits are made for the horizontal magnets 3H B . . . 8H B of the second stage switch. These magnets are associated one for one with the vertical magnets 4V A . . . 9V A of the first stage switch. The operated state of a V A contact indicates that the associated link is busy and disables the corresponding horizontal magnet H B of the second stage switch. Selection of a link is then effected by the operation of the quickest acting H B magnet in the isolated portion of the chain. An alarm circuit comprises a relay PRI whose differentially wound windings are normally operated over the hb contact chain and the d contact chain, so that failure of one of the contacts unbalances the relay to cause it to operate. The ha contact chain is also tested by relay PRII whose release brings up an alarm. PRII is prevented from releasing by a contact n when the chain is in use. Arrangements are also shown for increasing the number of link circuits, by providing an additional cross-bar switch providing two extra links for each subscriber, the modifications for the chain circuit being indicated.