Active Redundancy: Both components operate all the time but only one is needed.
Failure occurs only when both fail or (EP1)*(EP2)
Thus reliability is: Rs = R1 + R2 - R1*R2
Example: Use two components and both components have a reliability of 0.90.In a series| Rs = .9*.9 = .81 (above)Redundant| Rs = .9+.9-.9*.9 = .99Two redundant components in a series| Rs = .99*.99 = .98