An apparatus for detecting relative positioning of medical devices located within a human body, the apparatus comprising an inner elongate member comprising a plurality of electrodes and a first sensor member, where the first sensor member is located a known distance from each of the plurality of electrodes, and an outer elongate member comprising a first sensor, and an outer sensor member located between the first sensor and an inner wall of the outer elongate member, where the inner elongate member is configured to move within the outer elongate member and the first sensor is configured to sense a signal generated by movement of the inner elongate member relative to the outer elongate member, and a position detection module including an electronic control unit configured to detect a position of the first sensor member relative to the first sensor based on the signal.
