Patent GB-1077679-A (GB)
Title: Improvements in or relating to apparatus for use in telecommunications systems exchanges
IPC: H04Q3/00
Filed: 1965-08-11
Abstract: 1,077,679. Automatic exchange systems. SIEMENS A.G. Aug. 11, 1965 [Aug. 12, 1964], No. 34317/65. Heading H4K. In an exchange system including a route simulation network utilized for route selection through an associated switching network, marking of an inlet causes all free paths to all free outlets to be obtained whereafter one outlet appertaining to a desired direction is selected on the basis of a predetermined order of priority of these outlets and then a unique path to this outlet is selected. The outlets are trunks to other exchanges, some of the trunks being first choice routes others being overflow routes (involving tandem working) to any particular exchange. The outlets are graded in differing orders of accessibility. Tne switching network is composed of four stages of relay switches arranged in groups such that an A switch has access only to B switches within its group whereas all B switches have access to all C switches, the latter then having access to D switches within a group (Fig. 2, not shown). The trunks of each route are distributed among the outlets of the D switches. The pathseeking network utilizes conventional marking centre techniques with contacts in the links between centres controlled by busying relays in the interstage links of the switching network. Separate energizing and holding paths are provided in the switching network, both paths having negative battery at each end with an earth connection at their centres, i.e. in the BC links (Fig. 3, not shown). During growth of the exchange there may be more than one link between any two switches of adjacent stages and these links are selected for a call on a priority basis using relay chains in the intercentre links. Selection of an outlet (Figs. 5, 6).-The test leads of all trunks are brought out to points such as Ltg1 to Ltg 60 (Fig, 5) which correspond to the 10 outlets from each of the 6 D switches forming a group, so that for n groups there are n arrangements of test points Ltg. Corresponding outlets in each switch are arranged in columns VB1 to VB10. As shown VB1 is a complete column and in group n may represent all direct routes to an exchange X and in group 1 some of the routes to an exchange Y. VB2 is a split column and at its portion VB2a in group 1 represents the remaining routes to exchange Y while at VB2b in group 1 it represents some direct routes to an exchange Z. The other columns are graded similarly and may be split in different ways in each of the groups. The columns are connected through a cross-connecting field to points vpl to vp(m-1) leading to a common marker (Fig. 6). In the latter, the points vp are connected through a coupling field RV2 and " pre-test " relays V1 to V5 to earth while another coupling field BV1 connects the coupling relays AN of the n arrangements via contact chains of the V relays to earth. During selection, contacts 1wp1 to 10wp6 of all free outlets in all the n groups close (Fig. 5) due to the initial path selection process and in the marker a route relay ZP and a start contact cb operate. Consequently the coupling relay AN in the test arrangement having the first free outlet for this route energizes so as to connect this arrangement exclusively to the marker. One of relays V1 to V5 comes up so as to indicate which column or part of a column has been selected in the chosen testing arrangement. Contact chains formed by relays ZP and V and the coupling field RV3 now cause energization of one of the marker relays M1 to M10 (Fig. 5) whereby the test points of the selected column are connected to selection relays P1 to P6 (PK came up with AN). If the column is split, rectifier matrix G and coupling field RV4 ensure that earth potential is only applied to those selection relays P which are eligible. Consequently the first free outlet of this column causes operation of an eligible P relay which marks those links in the path seeking network that extend between the chosen D stage marking centre and the various C stage marking centres (Fig. 4, not shown). A relay chain then selects one of these links. Since the A, C and D switches have now been selected, the B switch is automatically identified and after first testing that a simultaneous connection to the chosen outlet is not being attempted the marker causes the selected path to be switched through and the various common apparatus to be released.