Its dead simple - surprisingly hard to find in a water timer. It runs on time without problems for 6 months now even after power blips out. One important thing to note is how many zones you need. I made the mistake of getting a 12 zone when I really only had 6 wired and only use 3 out of them due to drought. Speaking of drought, if you have restrictions in your area where you can't water after rain fall, there is a rain delay button making it perfect for my area.