a quantitative characterization of the reliability of technical devices. A reliability indicator may be individual or composite, depending on the number of properties it characterizes. An individual indicator corresponds to a single property, such as the failure rate. A composite indicator —for example, the operational readiness—corresponds to several properties. The indicators of devices that do not undergo repairs are numerical characterizations of their random operating time to failure. The indicators of devices that undergo repairs are characterizations of the corresponding random failure rates.
The indicators most frequently used in practice are the average operating time to failure, the probability of failure-free operation during a specified time interval, the mean cycles between failures, the average failure rate, the operational readiness, and the technical use factor.