GB1433648A - Switching networks for telecommunications exchanges - Google Patents

Abstract

1433648 Automatic exchange systems PLESSEY CO Ltd 9 April 1975 [26 April 1974] 18310/74 Heading H4K The matrix switch of Specification (App. 54200/73) having multistage networks as its crosspoints is modified so as to be capable of switching 4/4, 2/2, 2/4 and 4/2 wire connections. Fig. 1 illustrates the simplest case where the top left network NC11 switches 16 groups of 15 trunks on a 4 wire basis. In order to permit the connection of the incoming 4 wire trunks to two-wire outlets the top horizontal row multiple has 4/2 wire converters HA connected therein. Similarly to permit 2/4 working the leftmost vertical multiple has converters HB incorporated therein. The network in the opposite corner of the matrix viz NC2.2, as well as the crosspoint networks in the row and column containing NC2.2 are compulsorily of 2-wire type. Fig. 2 uses internally multipled (i.e. multipled AB links) blocks of networks AB1, AB2, AB3 for its crosspoints (details are given in App. 54200/73). It is necessary in this case therefore to provide converters HC or HH in each of the sets of trunks having appearances on the blocks and located between the 4-wire switches viz NC1.1 and the 2-wire switches. If NC1.2, NC2.1, NC2.2 are to be of 4-wire type these converters are moved to positions P and R while additional converters must be inserted at Q and S. Positions T, U, V, W, X, Y denotes the locations for converters when only the lowermost and rightmost switches are of 2-wire type. In a modification (Fig. 3) two of the blocks AB2, AB3 at crosspoint NC1.1 are of two wire type. The internal multiple must then incorporate converters HM while only the 4-wire terminations on AB 1 require converters HK and HL in the row and column multiples. It should be noted that a separate 2-wire C switch is required for overflow working in respect of the AB2, AB3 blocks. Fig. 4 (not shown) illustrates the case where only AB3 is NC1.1 is of two-wire type.