Explorer
Hold the tilt switch on "down" for 5 seconds while turning on the control panels main power. Follow the calibration instructions that will appear on the small LCD Display.
Pro 3 / Pro 3 GTO / Deep Blue
Hold the mode switch on "calibrate" for 5 seconds while turning on the control panel main power. Follow the calibration instructions that will appear on the small LCD Display.
Pro 4
No calibration is required.