A switch which is magnetic pole insensitive is described. The switch includes a Hall effect sensor coupled to a threshold circuit which provides an output signal indicative of the proximity of a magnet, and hence a magnetic field, to the Hall effect sensor regardless of the orientation of the magnet...http://www.google.com/patents/US6622012?utm_source=gb-gplus-sharePatent US6622012 - Magnetic pole insensitive switch circuit
