Circuit reliability (also time availability) (CiR) is the percentage of time an electronic circuit was available for use in a specified period of scheduled availability. Circuit reliability is given by

T s = T a + T o {\displaystyle T_{s}=T_{a}+T_{o}}

where T o {\displaystyle T_{o}} is the circuit total outage time, T s {\displaystyle T_{s}} is the circuit total scheduled time, and T a {\displaystyle T_{a}} is the circuit total available time. In addition, circuit reliability is the expected lifespan of operation of a functioning system under nominal conditions.

This article incorporates public domain material from . General Services Administration. Archived from on 2022-01-22. (in support of MIL-STD-188).