Patent GB-1021818-A (GB)
Title: Switching network
IPC: H04Q3/52
Filed: 1964-03-20
Abstract: 1,021,818. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. March 20, 1964 [March 25, 1963], No. 11851/64. Heading H4K. [Also in Division H1] Multi-stage cross-point switching networks are constructed out of printed circuit cards carrying the matrices. The networks are said to be designed to have occupation values of interstage paths which, for a given grade of service and traffic volume, require the total number of cross-point devices (PNPN transistors) to be a minimum. The networks are also said to be capable of expansion at a linear cost per added increment of line capacity. In the 100 line network of Fig. 2 ten 10 Î 5 primary matrices are followed by five 6x10 secondary matrices. Half the horizontals of the secondary matrices are graded over 45 to the originating sides of links 21 the terminating sides of which have access to the other half of the horizontals of the secondary matrices by way of a tertiary matrix 33 and a grading panel 46. Trunks are connected over the tertiary matrix which always has one vertical per link and trunk and has at least as many horizontals as verticals. The number of tertiary verticals is never greater than three times the number of equipped secondary matrices. Fig. 3 shows a stack of printed circuit cards carrying crosspoints for the primary and secondary matrices. Each card carries a 10x 7 primary matrix and seven verticals, one from each of a possible seven secondary stage matrices. Cross-points for the secondary matrices are connected by printed strips to the edge of each card where terminals allow the verticals of corresponding matrices to be connected by horizontal cabling such as 57, 58. Fig. 5 shows a 200-line network made up of two of the 100-line networks of Fig. 2. The two 100-line networks share a single group of link circuits 21 which are multipled to the grading cards 45a, 45b. Trunks and originating sides of links are shared by two tertiary matrices 68, 69 which are split by way of grading cards 46a, 46b between the two 100- line groups. The tertiary matrices are preferably each mounted on four printed circuit cards. The grading cards are preferably drawn from a stock classified to meet varying requirements. A 1000-line switching network, to satisfy the design conditions, is organized with A and B switching matrix stages following the primary and secondary stages as shown in Fig. 6. Two groups of four 100-line networks, H1-H4 and H5-H8, and one group of two such networks, H9, H10, are combined with access to a common register 109 over a connector 111. Only the terminal members of network H1- H4 are shown with network H10 of the last group. Each group'has a set of links such as 21a, 21b, the originating sides of which are multipled over the 100-line networks of each group by way of grading cards, such as 133, to connect with outlets of the A matrices. Terminating sides of links together with trunks 108 are connected over distribution frame 117 in multiple to the B matrices. Since, for all purposes, the A and B matrices are not conveniently provided on printed circuit cards, each of which is large enough to accommodate an entire A matrix and enough to comprise an adequate B matrix, extension cards may be plugged into the edges of the A matrix carrying cards so as to extend the size of the B matrices. On the other hand, unused links between A and B matrices may be connected to used links to extend the capacity of equipped B matrices by the use of plug-in printed circuit cards which provide the necessary multiple connections.