US Patent 7768367 Circular magnetic switch

A circular magnetic switch comprises a circuit device and a ring. The circuit device is provided with a plurality of magnetic induction elements and the ring is provided with a plurality of circularly arranged magnets, so that the magnetic induction elements are able to sense the relatively positional changes of the magnets when the ring is turned. The circular magnetic switch is characterized in that: at least an anti-interference magnet is further provided between at least two magnets of the plurality of magnets and the polarity of two magnets is opposite to that of the anti-inference magnets that is provided between the two magnets.