Redundancy (engineering)
In engineering, the duplication of critical components of a system with the intention of increasing reliability of the system is called redundancy. In safety-critical systems, such as fly-by-wire aircraft, some parts of the control system may be triplicated. An error in one component then may then be out-voted by the other two. In a triply redundant system, the system has three sub components, all three of which must fail before the system fails. Since each one rarely fails, and the sub components are expected to fail independently, the probability of all three failing is calculated to be extremely small. See safety engineering.