Patent ID: 7307824

Claim:
An apparatus for providing a signal indicative of the proximity of a magnetic article, comprising: a magnetic field sensor for providing a magnetic field signal having a level proportional to a sensed magnetic field and a polarity that is a function of the polarity of the sensed magnetic field; and a detector responsive to the magnetic field signal for providing a detector output signal indicative of whether the magnetic article is within a predetermined distance of the detector regardless of the orientation of the magnetic article relative to the detector, the detector comprising: a comparator responsive to the magnetic field signal for comparing the magnetic field signal to a first threshold level and a second threshold level to provide the detector output signal at a first signal level when the magnetic article is within the predetermined distance of the detector regardless of the polarity of sensed magnetic field, wherein the comparator comprises a window comparator operable to provide the detector output signal at the first signal level if the magnetic field signal is either greater than the first threshold level or less than the second threshold level and at a second signal level if the magnetic field signal is less than the first threshold level and greater than the second threshold level, wherein the first threshold level changes to a third threshold level in to the detector output signal changing from the first signal level to the second signal level and wherein the second threshold level changes to a fourth threshold level in response to the detector output signal changing from the second signal level to the first signal level; and a single circuit for establishing the first threshold level and the second threshold level.