Patent GB-1345824-A (GB)
Title: Telecommunications exchange systems
IPC: H04Q3/54
Filed: 1971-12-17
Abstract: 1345824 Automatic exchange systems SIEMENS AG 17 Dec 1971 [18 Dec 1970] 58834/71 Heading H4K In a multistage switching network through which paths are selected with the aid of a memory map, the links between certain stages are simulated by a guide wire network through which the information from the map is passed so as to eliminate the need to logically manipulate the data in order to discover a particular free path. Trunking (Fig. 1).-The network is of the folded type and consists of four identical sections KG1-KG4 which are linked in a highly symmetrical manner at their right-hand sides. Intersection calls obviously are set up via these links. Intrasection calls are set up by closing two crosspoints of a same outlet of a particular last stage switch. This means that those intersection links connected to so-used outlets will be busied even though they are not actually involved in carrying conversation. Each of the four sections KG comprises a twostage folded network having in its A stage ten 10 Î 8 switches KVA (1-10) to which inlets T are connected and six 8 Î 8 switches KVA (11-16) to which outlets R are connected, and, in its B stage, eight 16 x 8 switches. The first two outlets of each B switch are not linked to any other section so that they are always available as first choice outlets for intrasection calls. The third and fourth outlets of each B switch in the first section KG1 are linked to the third and fourth outlets of the correspondingly numbered switches in section KG2 as indicated by the link bunch 3434. Similarly outlets 5 and 6 are connected to outlets 5, 6 in section KG3, and so on. In the case of section KG2 its 7, 8 outlets are connected to outlets 5, 6 in section KG4 (link bunch 7856) and for section KG3 its 7, 8 outlets are connected to outlets 3, 4 in section KG4 (link bunch 7834). Path simulator. Fig. 3.-Each of the intersection links emanating from correspondingly numbered terminals of the B switches in a same section, e.g. 175 to 875 from terminals 7 of B switches in KG2 (Fig. 1) are provided with a single path finding wire, e.g. 75f. Since each section is connected to the others by two parallel links, e.g. 186 to 886 and 175 to 875 in the case considered, the corresponding guide wires 86f and 75f are grouped as at 7856f. The terminations f1-f8 for the guide wires are actually provided in the network sections by means of the connector strips which are used for terminating the links so that they may be wired up at the same time and in the same manner as the links to which they correspond. Guide wire outlets f1 and f2 are left unconnected since there are no links corresponding thereto. Operation (Fig. 2).-Intersection call central control 2ST is apprised of the caller's identity and so inserts this in terms of the section and switch to which the caller is connected into an input register ER of a memory map SP. The latter on its outlets 1-8 thereupon applies a free or a busy marking in respect of the eight outlets from the caller's A switch. At the same time ZST closes the V contacts corresponding to the caller's section and the r1 contacts so that the output of SP can be written into a register R1. Having done this the central control opens all these contacts, supplies the called party's identity to ER and closes the newly relevant V contacts and the r2 contacts so that the free/busy states of the outlets of the called party's A switch are entered into a register R2. It will be remembered that the network is highly symmetrical so that for a path to be set up correspondingly numbered B switches will have to be used in both sections. This further means that correspondingly numbered outlets of the A switches will also have to be used. Hence it is sufficient to compare the contents of the correspondingly numbered compartments of registers R1 and R2 in order to find a pair that are both free-this being effected by comparator V, and then to select one pair with the aid of W and finally to pass the resultant information, which is effectively the identity of a B switch in each section, to central control ZST. Thereafter ZST inserts the identity of the caller's section and the just chosen B switch into ER and closes the relevant v and rl contacts so that the free/busy states of the eight outlets from this switch may be entered into register R1. This accomplished, ZST inserts the identity of the called party's section and the same numbered B switch into ER and closes the relevant w, z and r2 contacts so that the free/busy states of those and only those outlets of this B switch which have access to the chosen B switch in the caller's section are entered into register R2. With the arrangement described there are at most two such outlets, V and W choose one of them if possible and inform ZST. If neither are available ZST reverts to the test for a free pair of B switches and then retries for a free link between them, With no success after trying all the switches busy tone is reverted, otherwise a path corresponding to the selected links and switches is set-up in the usual manner. Operation (Intrasection call).-This proceeds in a similar manner to that just described with the obvious difference that there can only be one B switch (i.e. A outlet) initially chosen and this lies in the section through which the call is being set up. In determining a free outlet of this B switch it has to be determined whether the linked B switches in all the other sections are free. Consequently after the R1 register has been set up with the free/busy states of the chosen B switch, ZST feeds the identity of the correspondingly numbered B switches from the other sections into ER, closes the z contacts pertaining to the section being used for the call and enables in turn the w contacts pertaining to the other sections so that the condition of the outlets of the B switches in these sections that are linked to the considered B switch may be entered into the R2 register. Since outlets 1, 2 of any B switch are not linked to any other switch, ZST must cause the condition of these outlets for the considered B switch to be entered into R2 by an independent process, thereby ensuring that all the outlets of the considered B switch are taken into consideration by the comparator. The subsequent operations are then the same as for the intersection case. Faults.-In the event of a faulty switch or where the network is incompletely provided it is arranged that the map output is inhibited. This is effected by an inhibitor circuit provided on the basis of one per section of each of the eight output wires of the memory map SP, the inhibitors being enabled by switches controlled by the corresponding network switching matrices, be these A or B switches (Fig. 4, not shown).