A standby system with two repair persons under arbitrary life- and repair times

A continuously monitored one-unit standby system is perfectly repaired either by an in-house regular repairer within a predetermined patience time, or else by a visiting expert repairer, who repairs all failed units. For arbitrary life- and repair times, we present a procedure to find the limiting proportions of time the system stays in each state using extended semi-Markov processes, whence we can find other limiting characteristics.