A optical encoder, is an optoelctronic, electro-mechanical device that converts the angular position or motion of a encoder blade to an digital code. There are two main types: absolute and incremental (relative). The output of absolute encoders indicates the current position of the code-blade, making them angle transducers. The output of incremental encoders provides information about the motion of the encoder bladet, which is typically further processed elsewhere into information such as speed, distance, and position. Rotary encoders are used in many applications that require precise shaft unlimited rotation—including industrial controls, robotics, computer input devices (such as optomechanical mice and trackballs), climate controll units, and various user interfaces.