An apparatus for transferring power includes a sensor circuit for identifying a position of an axially-movable locking element. The axially-movable element is movable between a first position, which inhibits transmission of rotary power through the apparatus, and a second position that permits transmission of rotary power through the apparatus. The sensor circuit includes two Hall-effect sensors that are employed to sense a position of the axially-movable locking element and produce sensor signals that are employed to control a magnitude of the current that is output from the sensor circuit. A method of detecting an operating mode of a power transfer device that is configured to transmit rotary power is also provided.