Hall-effect speed sensors detect the rotary motion of any iron object with slits or protruding parts, usually phonic wheels and gears. They integrate a retropolarized Hall-effect chip that detects the magnetic field variations according to the full-empty position of the wheel, providing an output digital frequency signal. In the double output versions, by reading signals A and B the clockwise or anti-clockwise direction of the wheel can be determined. The phase difference between the two signals determines the direction of the rotation: in particular, the direction of the rotation can be established according to the delayed or advanced phase between two square wave signals, or through a switch signal. They find typical application on engines, differentials, transmissions, turbines, pumps and can operate under the most severe conditions with respect to temperature, pressure, vibrations, electromagnetic disturbances and external elements. The output signals are available in a wide range of configurations and diagnostics, including: the CAN BUS protocol, output current and the innovative "ALIVE" function.