4. Operational reliability

4.1 Definitions

Among the various qualities required of a telecontrol system, dependability is of paramount importance. This can be broken down into four main terms: reliability, availability, maintainability and safety.

• Reliability is defined as the ability to perform a required function, under given conditions and for a given duration. This ability is measured in terms of probability, taking into account the duration of the mission in question.

• The availability of a system is the probability that the system will not fail at the time under consideration, independently of its previous life.

• If the system is not repairable,...