One example of an alternating renewal process is a production process (or a machine) that works for a time Z1, then breaks down and has to be repaired (which takes a time Y1), then works for a time Z2, then is down for a time Y2, and so on. If we suppose that the process is as good as new after each repair, then this constitutes an alternating renewal process. It is worthwhile to note that in this example it makes sense to suppose that the repair time will depend on the amount of time the process had been working before breaking down.