where x is the logic value of the logic variable in the
normal condition and xf is the logic value of the logic
variable in the faulty condition. The logic value xf is
determined irrespective of any fault in the logic level
Zai (i = 1, ..., m) that provides the logic value x =
CZai (or depends only on the number of faults) and
can essentially become a majority operation signal.
An upper value indicates a fault-less condition and
thus can serve as safety information.
Multide-Valued Operation bv Window Comparators
The window comparator defined by Eq. (3)
indicates that if the multiple-valued input x is made
binary and the binary output signal is subjected to
binary logic operation, the results opened can be
reconstructed as a meaningful multiple-variable
output signal by Eq. (4) or (5). Let the multipleinput
vector x be as given by
and let F(x) be the operation system, including the
window comparator, and Fk(x) (k = 1, ...,4T)h.e n,
the multiple-valued operation using the window
comparator can be illustrated as shown in Figure 2.