Patent GB-1033094-A (GB)
Title: Improvements in or relating to a method and apparatus for selecting and establishing a free transmission path through a plurality of stages of switching multiples
IPC: H04Q3/00
Filed: 1964-02-03
Abstract: 1,033,094. Automatic exchange systems. SIEMENS & HALSKE A.G. Feb. 3, 1964 [Feb. 4, 1963], No. 4576/64. Heading H4K. In an exchange system comprising a multistage switching network and a route-selection network which simulates the switching network, a path between an inlet and outlet of the switching network is selected by applying marking potentials to the corresponding inlets and outlets of the route selector whereby the markings pass via all possible free routes to a first position in the network whereat one possible section of a route is selected in response to the markings and wherein transmission of the marking from a second position in the network to the first position is then inhibited while a reverse marking is transmitted from the first to the second position so that at the latter position a further section of the route may be selected, this process being repeated until a unique route is selected. As described, the first and second " positions " correspond to stages of the switching network and the " positions " are interconnected by conductors corresponding to interstage links. At each " position " a socalled " marking centre " is provided in respect of each co-ordinate switch of the corresponding stage. It is suggested that the " positions " may correspond to links and the conductors to switching stages but this alternative is not particularly described. The speech path corresponding to a selected route is set up as described in Specification 897,677. The switching network may comprise crossbar, cross-coil or relay switches arranged as shown in Fig. 1. One possible speech-path between an inlet Tlj and outlet Z11 of the switching network is shown in Fig. 2 wherein, for example, contact 1ka1j1 represents the crosspoint interconnecting the jth inlet and the first outlet of the first co-ordinate switch of the A stage. Route selector.-As shown in Fig. 3 the first position is located at the centre of the network, i.e. the D-stage, the second and third &c. positions then being symmetrically arranged thereabout. The marking centre fDn shown at the first position corresponds to the nth D switch. To select a free route, positive potentials are applied to the inlet ltlj and the outlet 1z11 of the network whereby at the first position each free marking centre which receives these potentials supplies a signal from its AND gate Udn to a one-at-a-time selector KVD. The latter then returns negative potential to the selected centre and removes a positive potential from its outlet x. Consequently all gates Uel of the marking centres fE1 in the second position are inhibited whilst those gates Sel which receive the negative potential transmitted from the first to the second position and the positive potential transmitted from the outlet 1z11 conduct. Again a selector KVE selects one of these marking centres, applies negative potential thereto and removes positive potential from its outlet z leading to the next position. This process is repeated up to the outlet of the network and preferably a similar process goes on simultaneously towards the inlet 1t1j. Decoupling diodes, e.g. Gdeln, are included in each of the link-simulating conductors f and the contacts, e.g. bdcln are opened or closed in dependence upon the busy or free condition of the associated links. In an alternative arrangement (Fig. 4) a positive marking potential is transmitted by each selector, e.g. KVD, so that in this case additional and oppositely-poled, decoupling rectifiers are required. The gate SUe1 may be inhibited (when gate Uel is conducting) either by a signal applied from the output or, as shown here, from the input of gate Ue1 A further arrangement using only rectifiers and inverters, e.g. common emitter amplifiers, is described with reference to Fig. 5 (not shown). A non-symmetrical switching network and its corresponding simulation network is described with reference to Figs. 6 to 9 (not shown). A method of connecting a plurality of marked inlets to one or more marked outlets which is similar to that disclosed in Specification 897,676, is also described.