Patent GB-1264922-A (GB)
IPC: H04L12/52
Filed: 1970-02-04
Abstract: 1,264,922. Telegraph exchanges. SIEMENS A.G. 4 Feb., 1970 [5 Feb., 1969], No. 5312/70. Heading H4P. In an electronic exchange system particularly for a teleprinter network, the switching functions are controlled by a programme unit exchanging information from a store in which each feeder is permanently allocated a cell in the store for the accommodation of a word, designating a particular trunk and the direction of the last polarity change on the feeder associated therewith, each word is sampled by the programme unit at specific time intervals, the count being raised by " 1 " in the presence of one of the two possible directions of the last polarity change, disconnection being initiated when a predetermined count is reached. Information characterizing the feeders is stored at a storage position permanently assigned to each feeder and is only tested and modified by the programme control when information requires monitoring.  In Fig. 2, control lines used in a conventional manner for interconnecting registers also registers and the store have been omitted; lines used for parallel transfer of store words are marked with thick lines and control paths by thin lines.  A store application control SAFS is connected to a line terminal unit LF, programme control PSt and a store operations control SAPS. Controls LE and PSt communicate with store SP via word input and output registers WER, WAR the contents of which are combined in OE. The controls also carry out store operations i.e. polarity check which are recorded in the relevant feeder cells within a store cycle in store Sp. A store processing control SST, which decodes the content of register OPR controlled by PSt, LE, the latter having a routed access directed by SAFS and address register ARS, determines the nature of the operation effected by operations equipment OE. Unit SAFS also assigns the next store cycle and opens transmission paths through lines L1, L2. Programme control PST includes address register ARP, word register WR, command register BR, a decoder D, a counter BZ, a logic test system PL for testing and modifying a count stored in the feeder cells in stores SP, and a control VUE1 for sampling feeder cells. The address of the feeder cell to be sampled is contained in register AZR and the address of a disconnection instruction is transferred to another register APR. The feeder cells have additional bits for continuous polarity testing. The programme control samples all feeder cells cyclically with specific intervals dependent on the duration of the potentials to be monitored e.g. for 300 m./sec. disconnect signals the interval may be 120 m./sec. During a sampling operation the content of the relevant feeder cell is transferred to a word register where it is tested by the programme control. If the count has not reached a determined amount and the polarity is correct the count is increased by "1". Subsequently the stored word is recorded back in the relevant feeder cell with the count modified. A polarity change resets the counter to "0" hence the count can only reach the determined limit if the line potential is constant. If the programme control detects that the max. count has been reached, disconnection of the relevant connection is initiated.  The feeder cells are arranged in the form of a block having a fixed store address, each feeder being assigned two cells, one of four-bit capacity containing data for the transmission of polarity changes, and the other for connection monitoring. To obtain the address of the next feeder cell the preceding cell address must be increased by 2.  Sampling of a group of feeder cells is started by a pulse train lasting 3À75 m./sec. from pulse generator TG which initiates the recording of the start address ADR in the counter BZ. The sampling command is issued by VUE1 and is ended when a group of feeder cells has been sampled this being determined by a counter (not shown) monitored by PL. After sampling, content of BZ is increased by PL and transferred to ARP. If by testing register WR, system PL detects an impending disconnection condition, the content of counter BZ is increased by PL and the address of the relevant feeder cell is transferred into APR. The system is described in greater detail in connection with Figs. 5-8 (not shown).