Liquid level sensor (on/off switch) float. It has a float equipped with a magnet that moves vertically along the guide tube under the influence of the buoyancy of the liquid, causing the reed switch to close or open. They are usually mounted in the bottom or lid of the tank. It can be used to control the lower or upper liquid level. By changing the position of the float, the function of the reed switch is changed from normally open to normally closed. The sensor can be used for various types of liquids, e.g. water, sewage, oil.