"gSerially operating data protection system - has bistable flip=flop changing state with first information bit in specified way in presence of parity bitEP0023821A2 *Jul 31, 1980Feb 11, 1981Fanuc Ltd.Apparatus and method for checking a memory and a computer system including a memory and apparatus for checking the memoryEP0033067A1 *Jan 8, 1981Aug 5, 1981International Business Machines CorporationPr" . . . . . . .