It consists of a float connected to a pointer through a rope via a set of pulleys. The pointer glides over a calibrated gauge board, positioned parallel to the tank. The float accurately follows liquid level variations in vertical direction. The horizontal float movement is restricted by two guide wires firmly anchored to tank bottom. As such, the pointer is in 'TOP POSITION' when tank is 'EMPTY' and in 'BOTTOM POSITION' when 'FULL'.