A transducer comprising a fixed part and a mobile part which are mounted for relative motion about a given axis. On the shaft of the rotor part there is fitted a magnetized element consisting, for example, of an annular element diametrically magnetized at a single pair of poles. Mounted on the fixed part is a pair of Hall-effect sensors which are set angularly staggered by 90null about the axis of rotation of the shaft. The Hall-effect sensors generate corresponding output signals having values that vary in a continuous range. The values of the output signals generated by the transducer uniquely identify the relative positions of the aforesaid fixed and mobile parts with respect to the axis of rotation.