Patent GB-1067735-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04Q3/00
Filed: 1964-08-27
Abstract: 1,067,735. Automatic exchange systems. SIEMENS A.G. Aug. 27, 1964 [Aug. 28. 1963], No. 35085/64. Heading H4K. In a system utilizing a route simulation network for selecting a free path through an associated multi-stage switching network, one or more devices located intermediate the ends of the network and which are to be included in the selected path are marked in the simulator in such a way that during end-marking of the latter only those paths including the devices are available for selection. As described, the exchange system receives V.F. code signals from a calling subscriber whereby a trunk in the wanted direction is chosen and a D.C. sender (which " translates " the V.F. code into D.C. impulses) is allocated to the call whereafter it is necessary to interconnect the subscriber's line circuit, the trunk and the sender. The line circuits TI (Fig. 1) are connected to the inputs of the network, the senders Z to the outputs and the trunks Wn to intermediate points. In this way the last stages E, F of the network may contain fewer matrices and are releasable as soon as digit sending-or any similar temporary function-is completed. If more than one trunk and/or sender are available then these may all be marked and the simulator determines which ones of them should be used in a manner analogous to that of PBX final selector hunting. When a path has been selected, the simulator initiates the operation of the corresponding cross-points in the switching network (Figs. 5 and 6, not shown). Route selection.-The simulator is in general similar to that disclosed in Specification 897,676. However, in the network shown in Fig. 3 additional contacts 1wmn and 2wmn are included in the f and g wires corresponding to links between the D and E stages of Fig. 1. These contacts are normally open whereas the other contacts, e.g. 1bdemn and 2bdemn which correspond to free links, are normally closed. During selection, end-contact 1t1j and 1z11, lxi corresponding to the inlet and outlet concerned, are closed, whereby markings pass through all free paths towards a " matrix selector " KVC. Certain matrices in the D stage which have connected thereto the devices Wn which it is required to include in the speech path, are also marked by closing the contacts wmn. Consequently those of the AND gates Ucm, which correspond to C stage matrices simultaneously accessible from the input and output become conductive and selector KVC selects one of them. Markings are then passed forward and backward from the marking node gCm in the g wire. A B-stage matrix accessible from the marked input and the just-selected C-stage matrix is selected by KVB. In stage D one or more AND gates Udm are marked, depending upon how many additional devices were marked by the closing of contacts wmn. Consequently selector KVD chooses one of these and transmits the markings backwards through the E stages where a single matrix is again chosen. If more than one output stage matrix is initially marked selector KVF selects between them. If more than one output of an F stage matrix is initially marked then selector PKVF performs the final selection. If the devices are all connected to a single matrix in stage E, say, then an additional contact may be included in the marking node corresponding to this matrix (Fig. 4, not shown) and the additional contacts in the g and f wires are then dispensed with.