Patent GB-1262113-A (GB)
Title: Improvements in or relating to circuit arrangements for use in telecommunications exchange systems and in particular telephone exchanges, with test circuits for intermediate line testing
Inventor: THOMASCH SIEGFRIED
IPC: H04Q3/00
Filed: 1969-04-16
Abstract: 1,262,113. Automatic exchange systems. SIEMENS A.G. 16 April, 1969, No. 19313/69. Addition to 1,262,114. Heading H4K. In a system incorporating an at least 5 stage switching network, path finding is effected by injecting a high ohmic test potential into the holding wire of each link extending from the relevant input and output matrices of the network, detecting the potential at the other end of the link in the absence of low ohmic holding potential of opposite polarity to the test potential, repeating this procedure from those matrices of the second and penultimate stages which have just been found to have a free link leading thereto and so on until the central stage is reached whereupon one matrix thereof is selected from those matrices having a coincidence of a test potential on each side. With the system described, there is only one path between an inlet or outlet of the network and a matrix in the central stage. Details of the test potential and a detector therefor are disclosed in parent Specification. Trunking Fig. 1.-This is of the star type i.e. only one path, in respect of an inlet or an outlet and a central stage matrix. The AB and DE switches are grouped as shown, the A, B and C switches then being formed in sections T1 ... Tq which are fully accessible from the DE groups. Path finding, Fig. 2.-The marker is provided with details of the inlet T and outlet R which are to be connected and consequently closes the switches in Sabc and Scde which individually apply high ohmic positive potential +U, Wab and + U, Wde to the individual hold wires of the links emanating from the A and E switches to which the inlet and outlet pertain. Each of these links which is not busy i.e. does not have a low ohmic negative holding potential thereon, conveys the test potential to an individual detector Xab and Xde. These effectively define all the B and D switches which can be reached from T and R. All the operated (relay) detectors Xab and Xde close their contacts xdb and xde so as to apply the test potential to the hold wires of the individual links emanating from the first marked B and D switches whereby in the C stage at least one of the gates U respectively associated with the C-switches will be opened by a coincidence of test potentials on its input so as to bring-up one relay XC in a one-only-selector chain. With R, T and a particular C switch now known, end and centre markings are applied to the seize wires so as to energize the relays in the path between R and T (Fig. 3, not shown), the path being held to negative battery at the inlet when the cross point hold contacts Ka etc. are closed. The possibility of dispensing with individual inlet hold contacts t2 is discussed with reference to Fig. 4 (not shown), which depicts the usual use of group contacts for defining a section, a group within a section and then an inlet within a group. The C-switches are arranged in sections as already mentioned and it is suggested that the detectors U, X could be commoned to corresponding switches in each section with a contact chain for defining a section, a group and a matrix during path finding.