Early attempts to apply data processors to tasks previously reserved for vital relays concentrated on redundancy and voting systems, essentially as protection against hardware failures. Not enough attention was devoted to software, as no complex program can be considered foolproof even after a lengthy period in service. LM Ericsson has favoured in parallel running of non-identical programs with multi-stage comparison to guard against wrong-side failures. This technique has been successfully applied both to large interlockings and to on-train signalling and speed control systems. Before long, the two functions of logic and output checking may be carried out within a single microprocessor, using fault-tolerant programming.
Computers can now perform vital functions safely
Zuverlaessige Ausfuehrung wichtiger Funktionen durch Computer
Railway Gazette International ; 135 , 11 ; 1004-1007
1979
4 Seiten
Article (Journal)
English
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