Rain STOP is an electronic rain sensor All its components are high quality electronics from Japan. Its working principle is studied to start to work immediately in case of rain Rain stop stops irrigation as soon as 4 mm of precipitation are reached, preventing the irrigation system from working while it is raining. Two different models of Rain stop are available: Rain stop 3 wires and Rain stop 4 wires. Rain stop 3 (three) wires allows to connect a rain sensor to all 24 vac controllers as it is not needed for its installation to have a sensor dedicated port, on the controller. Rain stop 4(four) wires is the professional rain sensor for the 24 vac controllers equipped with sensor control feature.