Issue No. 11 - November (1972 vol. 21)
T. Takaoka , Electrical Communication Laboratories, Nippon Telegraph and Telephone Public Corporation
Let S be a sequential machine with binary (i. e., 0 or 1) input and binary output. Suppose that the third value N, different from 0 and 1, represents the faulty input or output value. An N-fail-safe (NFS) machine S? of S is then defined as a sequential machine with ternary (i.e., 0, 1, or N) input and ternary output such that: 1) S is a submachine of S?, and 2) possible output failures of S? are 0?N or 1? N for any input failures 0?N or 1?N. This machine may be considered "fail-safe" since no failure such as 0?1 or 1?0 occurs in the output.
Asymmetric failure, fail-safe sequential machine, failure detecting circuit, half-weight code, information loss set, N-fail-safe sequential machine, one-weight code, state assignment.
T. Ibaraki, T. Takaoka, "N-Fail-Safe Sequential Machines", IEEE Transactions on Computers, vol. 21, no. , pp. 1189-1196, November 1972, doi:10.1109/T-C.1972.223476