Abstract: A detent mechanism for a manually activated transducer is disclosed in which the transducer element is movable along a predetermined path by means of a handle and includes a sensor for scanning markings on the transducer element and includes first and second components that determine the magnetic field in an air gap. These magnetic components have spaced, adjacent grooves directed in the direction of movement of the rotating transducer element. The magnetic forces created between these first and second components serve to hold the transducer element in one of a plurality of definite positions.