Abstract—In fail-safe computer systems, such as railway
signaling systems, the outputs directly drive some vital units.
Once they happen in error, there will be some injuries, even
losses or damages. In order to improve the reliability and safety
of fail-safe computer systems, in this paper, we innovatively
design and implement two kinds of 2-out-of-3 voters: the
dynamic voter and the static voter. The former achieves the
voting function mainly with pulse demodulation circuit, and the
latter realizes it mainly with four solid state relays. Furthermore,
we analyze their performances with Markov model. The dynamic
voter is hazard-free, and the reliability of the dynamic voter is
376 years. For so few components, the static voter is of amazing
reliability with 875 years. In addition, with the help of loopback
detection, it satisfies safety integrity level 4. At last, we analyze
and discuss some applications of the two voters in railway
signaling systems, and make suggestions on application choice.