Optical, magnetic  encoder, are an electromechanical device also called hollow shaft or shaft encoder, that modify the motion, angular position of an axel to digital or analog signal output. There are 2 types of encoders available on sale. The absolute encoder output is a transducer of the angle of rotation of the axis. It informs us about the absolute value of the processed angle. The incremental encoder processes information about the rotation of the shaft in typical applications. Such as the motion of the shaft, where the measurement of distance, speed and position is used. Optical or magnetic rotary encoders are used in a wide range of applications that require monitoring and control of the mechanical position of the shaft. They find application in industrial controllers, robotics, motors, machine tools.