Principle:-All float-operated liquid level controls operate on the basic buoyancy principle which states that "a body (float) immersed in a liquid is buoyed upward by a force equal to the weight of the displaced liquid". Operation:-This is a float-operated level switch having a single float for high or low operation enclosed inside the cage having side-side connections to the process tank. Here the float which carries the magnet moves up and down sensing the level increase or decrease inside the external chamber. These switches are externally fitted i.e. they are clamped outside the chamber pipe. These switches are latching type and they are either reed or micro type. Once the float moves up due to level rise while exceeding the actuation points the float magnet actuates the switch i.e. (NC to no). It remains as no contact because of the latching arrangement inside the switch though the level continues to rise to the maximum. When the level drops lower than the set point the contact changes through the level goes down even to its lowest position such as even to zero position.