Magnetic Level Indicators (MLIs) rely on a magnetic float that travels up and down with the liquid in a chamber, which is mounted to a pressure vessel or storage tank. The float contains a magnetic assembly that interacts with an externally-mounted visual indicator. As the float follows the liquid, the magnetic field causes highly contrasting flags in the visual indicator to rotate, therby displaying a highly visible representation of the level. Magnetically-actuated external point switches and continuous transmitters can expand the function of the MLI by providing high or low alarms, as well as real-time level data supplied to the control room (4-20mA, HART, Foundation fieldbus).