Reliability Improvement by the Use of Multiple-Element Switching Circuits

Physical devices used for switching have finite probabilities of failure. Circuits which make use of redundancy to achieve resultant reliabilities greater than that of their elements have been proposed and have been analyzed for the case of intermittent failures. The present paper extends certain of these results to the case of permanent failures of the elements, assuming that the reliability of these elements is known. It is shown that, for operating periods which are short compared to the mean time to failure of the elements, a substantial increase in reliability can be obtained by such redundancy.