2-Unit Redundant Systems with Replacement & Repair

The paper deals with redundant systems consisting of i.i.d. units with repair. There are 2 kinds of spare units 1) warm standby units with instant perfect replacement and 2) cold stock units which can be supplied after a delay only. The replacement mechanism and the derivation of the mean 'time to first system failure' (TFSF) using Markov renewal processes are illustrated on two models. The influence of stock unit replacement time on the mean TFSF is studied.