Abstract: An improved analog preprocessor for a jaw tracking device having a plurality of magnetic sensors (44), each of which produces a first analog signal corresponding to the position of a magnet fixed with respect to the patient's mandible. The preprocessor includes analog means (200) for electrically combining the first analog signals to produce at least one analog position signal representing the position of the magnet along one axis, a gain select circuit (302) for providing a gain select signal, a variable slope ramp generator that provides a ramp signal having a slope corresponding to the gain select signal, a comparator for comparing the position and ramp signals and generating an output pulse having a length corresponding to the magnitude of the position signal, and a low pass filter for receiving the output pulse and producing an analog movement signal having a magnitude corresponding to the pulse length.