Patent GB-1218701-A (GB)
Title: Improvements in or relating to telecommunication exchange systems
IPC: H04Q3/48
Filed: 1969-02-27
Abstract: 1,218,701. Automatic exchange systems. SIEMENS A.G. 27 Feb., 1969 [28 Feb., 1968], No. 10574/69. Heading H4K. In a four (or more) stage network in which the matrices of the AB and the CD stages are formed into a plurality of independent subnetworks, each having their own path finding network and in which full availability over more than one path between network inlets and outlets is obtained by appropriate trunking between the BC stages, the BC links are provided with their own path-finding networks which are connected to the first inputs of a set of 3 input AND gates whose second and third inputs are connected to the path-finding networks of the subgroups to which the relevant BC links are connected, whereby a unique path can be selected by marking the inlet and outlet of the relevant AB and BC path-finding networks and then making a selection of one only of those AND gates which are opened by the simultaneous arrival of three markings. Examples of 4 and 6 stage networks are described. In a partly equipped network there may be more than one link between a B switch and a C switch (see below). Trunking in 4-stage network, Fig. 2.-The AB subnetwork KG1AB comprises twenty, 6 x 10 primary matrices KV1A1-KV1A20 which are linked with full availability to ten, 20 x 20 secondary matrices KV1B1-KV1B10. The remainder of the trunking and the conventions used therein should be obvious from the Figure. Path-finding networks (Fig. 3 in conjunction with Fig. 2). Each subnetwork such as KG1AB is provided with an individual path finding network such as ZL1AB. The column of contacts 1a1-1a20 represent A switches KV1A1- KV1A20, a contact being closed whenever its corresponding switch has an inlet in calling condition. The row of contacts 1za1bl- 1za1b10 represent the ten links emanating from switch KV1A1, the open/closed condition of the contacts indicating the busy/free state of the corresponding links. Each column of contacts represents the B switch on which the links pertaining to the contacts terminate, viz. contact column 1za1b1-1za20b1 represents the links terminating on switch KV1B1. The likenumbered columns from each AB subnetwork are multiplied on to a common AND gate, viz. column 1B1 of subnetwork ZL1AB is multipled over decoupling diode re to the common vertical wire 1 (centre of Figure) which extends to the left inlet of AND gate u1 The CD subnetworks, e.g. ZL1CD are similarly arranged, their like numbered columns, e.g. 1C1 being multipled to the right inlets of the AND gates, e.g. ul. The free/busy states of the BC links emanating from subnetwork KG1AB are represented by contact matrix ZL1BC, wherein the rows, e.g. zb1c1/1-zb10c10/1 each represent the likenumbered links, e.g. the first from each B switch or to each C switch and the columns each represent the links from a particular B switch. The contacts 1gl-1g20 are selectively closed by relays 1G1-1G20 in dependence on the CD subnetwork having the called outlet. Operation.-Assuming it is required to connect an inlet of switch KV1A1 in subnetwork KG1AB to an outlet of switch KV1D1 in subnetwork KG1CD, contacts 1a1 and 1d1 are closed, whereby positive battery is extended via closed (i.e. free) contacts, e.g. 1za1b1 to the marking centres 1B1-1C10 and thence to the left and right inputs of AND gates u1-u10. Simultaneously therewith, that relay, 1G1, which corresponds to the marked outlet subnetwork, is brought up by the potentials extended via OR gates M1AB, M1 CD andinverting gate J1AB. Consequently, positive potential from a control circuit X is extended to the first row of the first BC link path finder ZL1BC, whereby the centre inputs of AND gates u1-u10 corresponding to free BC links are also marked. A one-only selector KVBC chooses one of the triply marked gates and supplies suitable operating potentials to the switches in the selected route whose identity is fully determined by a knowledge of the marked inlets and outlets and the selected AND gate. Faults.-If the marks on thes elected AND gate do not disappear after switching instructions have been sent by the selector, an alarm is given and the route finding network corresponding to the unremoved mark is cut-out of service by opening the relevant contact set i. Partially equipped network, i.e. more than one link between switches of successive stages.-Such a network has less than the designed number of (fully equipped) subnetworks. Consequently spare links from each AB subnetwork may be connected to spare inlets on each CD subnetwork in order to provide additional paths during growth of the network. Path finding is effected by making an initial choice of the group of links interconnecting two switches in the BC stages and then selecting one only of these links. The two selections are made with the assistance of control circuit X which in effect considers each subnetwork as a plurality of minor networks and by suitable markings on yx allows more than one G relay to operate. The latter can then be considered one at a time by closing contacts x1-x20 in turn (Fig. 4, not shown). Six stage network (Fig. 5, not shown).-The trunking in each subnetwork corresponds to the trunking for the A, B and C stages of the fall network shown in Fig. 2. Route finding in the centre (CD links) is then effected in a manner not unlike that in the case of " more than link between stages " (see above), wherein links from different sections of the C stage are considered in turn by the one-only selector, the construction (not shown nor fully described) of the control circuit X being somewhat more complicated, however.