The action range of the two floats of the double float switch is 10 mm. If the demand control range is large, two float switch combinations can be used, so that there is a large stroke to ensure that the pump does not start frequently. The double float switch can be used to control the liquid level of the water tank, pool, sink, fish tank, etc. (drain or water), or to make the upper and lower alarm switch of the liquid level. Normal water intake process activated by the float switch below, and the float switch above stops working. The drain is activated by the float switch above and the lower float switch stops working. The float switch cannot directly control solenoid valves or high-power relays, AC contactors, etc.A small relay(like HH54P) is needed for transition. The contacts inside are made of a reed switch with very high sensitivity.