Patent ID: 7536217

Claim:
A system comprising: a device that is swallowed and passes through a subject; a magnetic field generator generating a constant magnetic field and disposed in the device; a position transducer that includes a plurality of magnetic detectors, adapted to be disposed in fixed positions forming the vertexes of a cube relative to the subject outside the subject and detecting intensities of the constant magnetic field generated by the magnetic field generator; a reference device selector that selects one magnetic detector out of the plurality of magnetic detectors as a reference magnetic detector based on the detected intensities; a selector that selects specific magnetic detectors based on a selection result of the reference device selector; and a position processor calculating a position of the device in the subject based on a detection result of the specific magnetic detectors; wherein the specific magnetic detectors includes three magnetic detectors which are selected from the plurality of magnetic detectors disposed on axes orthogonal to one another at the reference magnetic detector.