Johnson Pump Ultima Switch Auto Control w/Mirus [36303]Ultima Switch New digital technology uses the Mirus field effect detector cells producing micro electrical fields that detect disruptions caused by water and fluids. Detector cells are totally sealed, are never in contact with the water, will not corrode and are not affected by oil or foreign debris. ULTIMA activates at a 50 mm (2") fluid level and deactivates at a 20 mm (3 4") fluid level. A 3 second delay prevents false starts. ULTIMA switch is