For any 240 volt equipment in Australia Standard A float switch is a great way to automatically turn any appliance such as a pump, on or off. A ball inside the tethered float switch simply changes position from top to bottom with the rising or falling motion it changes the floats angle, thus breaking or establishing the electrical circuit to turn the pump on or off Possible applications Wet cellars, automatically filling a pond when evaporation or leaks have reduced the water level. Automatically filling header tanks. Etc How they work: As the water rises, at a pre determined level the switch turns on the pump. Once the level has been reduced to the level you set Automatically turns On and Off Adjustable switching level Plugged models are simple to install (no electrician required)