Patent GB-1336382-A (GB)
Title: Centrally controlled telecommunciatisns exchange systems
Inventor: GREGAREK K-D
IPC: H04Q3/545
Filed: 1971-07-06
Abstract: 1336382 Program controlled exchange systems SIEMENS AG 6 July 1971 [7 July 1970] 31556/71 Heading H4K Route search data for a program controlled sectionalized switching network is stored in areas of the control store grouped according to network sections, the program for calling condition searches and connection processing being interleaved at arbitrary intervals with a program to find free terminal circuits, such as junction and service circuits, for preallotment so that, for at least some connections, route finding can be accelerated. The network, Fig. 1, provides an array of folded switching sections the terminals of which are served by respective control units TW1 to TWn. Subscriber circuits T and junctor and service circuits U are distributed over the network terminals so that each first stage switch K11 to Kmv terminates a variety of circuits. Connections may be set up between network terminals of the same switch by using the first stage A alone. Connections between more widely separated terminals involve the stages B and C as well as A. Network state data is recorded in storage areas corresponding to the n network sections. Each area has a first section devoted to the network data sufficient to set up short paths requiring the first stage A alone; for such paths preallotted circuits are not seized as their processing time is always short. A second storage section provides space for the data necessary for path finding within the corresponding network section. A third storage section records data relative to network terminal circuit conditions through which search is conducted for path finding generally and for the preallotment of circuits in particular. A fourth storage section records the addresses of circuits selected for preallotment. Path finding programs for connections other than short path connections are abridged by using preallotted circuits as and when such preallotments are available. Preallotment programs may be inserted following calling condition and path finding programs for which no calling condition or path finding matures and which consequently take little time. One area of the store is common to all network sections and records in respect of which section and what kind of terminal circuit the next preallotment will be undertaken. By this means preallotments are distributed cyclically over the sections of the network. If during a preallotment process the fourth storage section of an area shows that the circuit previously allotted has been seized a search is conducted in the third storage section and a free circuit of the required type is preallotted by recording its address in the fourth section. If no circuit of the wanted type is free in the section, or if no preallotment is called for, the process steps to the storage area of the next switching section. When a circuit has been preallotted, or when the search has continued for as long as is allowable, the address of the section to which the search has progressed is recorded to give a starting point for the next search.