Patent ID: 8049503

Claim:
A position detecting system comprising: a body-insertable apparatus disposed in a state where it is introduced in a subject in a detection space; and an external apparatus disposed on the outside of the subject, wherein the body-insertable apparatus comprises an oscillation circuit that outputs an induction signal of a resonance frequency; a resonance circuit that generates a resonance magnetic field having the resonance frequency in accordance with the induction signal output from the oscillation circuit or a drive magnetic field having the resonance frequency generated in the detection space, and is connected between the oscillation circuit and a ground line; and a first switch that connects and interrupts the resonance circuit and the oscillation circuit or the ground line, the external apparatus comprises a drive coil driving unit that outputs a drive signal having the resonance frequency; a drive coil that generates the drive magnetic field in the detection space in accordance with the drive signal; a second switch that connects and interrupts the drive coil driving unit and the drive coil; a magnetic field sensor that detects the resonance magnetic field; and a position deriving unit that derives position information of the body-insertable apparatus by using information of the resonance magnetic field detected by the magnetic field sensor, the second switch connects the drive coil driving unit and the drive coil when the first switch is in an off state, and disconnects the drive coil driving unit and the drive coil when the first switch is in an on state, and the resonance circuit generates the resonance magnetic field in accordance with the induction signal or the drive magnetic field.