ABSTRACT
Output decision circuits like majority operation
circuits are required in the final stage of redundant
systems like fault-tolerance systems. The output
decision circuit must be a single redundant system
that is high in reliability and capable of quickly
detecting and reporting faults. This paper proposes a
fail-safe majority operation circuit with the
capability of immediately reporting faults by
utilizing multiple-valued signals and clarifies the
concrete configuration of the fail-safe majority
operation circuit. The fail-safe majority operation
circuit is defined as a circuit that has majority
operation output signals and fault inspection output
signals, never produces an output signal 1 in the
event of any fault in its component devices when the
operation output should be 0, and produces no wrong
inspection output signals even if one input signal is
erroneous. The fail-safe majority operation circuit is
comprised by fail-safe AND gates that have threshold
values and are called window comparators.