Patent GB-1230292-A (GB)
IPC: H04Q1/22
Filed: 1969-04-24
Abstract: 1,230,292. Automatic exchange systems. SIEMENS A.G. 24 April, 1969 [25 April, 1968 (2); 26 April, 1968], No. 20875/69. Heading H4K. Testing of the switching network and control circuits in a marker-controlled PBX is effected by a test desk which supplies the marker with specific details of a path to be set-up, the path comprising a first connection from an exchange line to a subscriber, a second connection from the subscriber to an internal relay set and a third connection from the relay set to a test position allotted to the subscriber. In addition, the relay set is connected via a register finder to one of a plurality of registers so that the number of, e.g. the test position, may be artificially dialled into the register from the test desk via the second connection. The exact nature and sequence of each test is determined by a programme. If there is any interruption exchange equipment an alarm (lamp) is operated, the sequence being restarted by a manual override (details of this feature are not given). It is assumed that the network is of the startype, viz. only one path between a defined inlet and outlet, and that the exchange lines are bothway trunks. The nature of the path finders is not discussed. In order to start a test, the test desk programme unit P applies a start potential to a link selector Z-E-AB. This comprises a chain of eight relays which is stepped through cyclically four times so as to mark in turn all the, e.g. 32 links between the A and B stages. If it is not required to test certain of these links then the relays corresponding thereto are marked busy by manually-operable keys in the selector. No provision is made for automatically indicating to the selector the free/busy state of the links or for stopping the test if it is later found that a selected link is already in use for a normal connection. A link, e.g. ZL1 for an incoming connection is found first and its identity is stored in another relay chain whereafter links, e.g. ZL8 and ZL32 are found for the second and third connection parts of the test path, the identities of these links also being stored. The group of AB links accessible to the predetermined subscriber are indicated to the relay selector chain which serves to find a link for the second part of the test connection. By some undisclosed means a subscriber simulator Tn-Si then marks a line circuit TA having access to the first selected link ZL1, the accessibility of the line circuit to the second link ZL8 having been ascertained as just mentioned. A CD link selector then chooses a pair of links for the first and third parts of the test path in a similar manner, while an exchange line selector An-P chooses an exchange line circuit AU. Finally a register selector Reg-E which comprises a transistor chain as well as a relay chain memory, chooses a register, a register finder U and an internal relay set HU. The registers allottable to the chosen relay set are connected thereto in sequence during each test connection, testing being interrupted, if any one of the registers is busy, until it becomes free. Again, registers &c. which it is not required to test can be ignored by manual operation of a key set. The normal path finders WS-ABC, WS-CD are caused to hunt in the usual way but since only the preselected links are marked free, the path finders should choose these links if they are fault free. Thereafter the first, second and third parts of the test connection are switched through in turn by the normal exchange markers An-TA, An-AB, An-CD and Reg-S. The subscriber Tn is not rung during the test. The subscriber simulator Tn-Si "dials" into the register over the second path, i.e. ZL8. The third part of the test connection (from HU to TP) may be set up by the normal exchange apparatus in response to the digits received in the register. As soon as all the tests are finished in respect of this connection, the test link selectors are restarted and a new connection is set-up. Specific examples of the relay chain and transistor chain link selectors and memories and the relay chains for signalling to the path finders the "identiy" of the preselected links are described with reference to Figs. 2-11.