This output code is called “Quadrature” because it repeats itself every four positions. It can also be shown in a “Truth Table”. Quadrature encoders are also called INCREMENTAL encoders. A microprocessor chip that reads a quadrature encoder can only determine the direction, clockwise or counterclockwise, and the amount of increments, that the encoder shaft has been rotated. A microprocessor cannot determine the absolute rotational position of the shaft. This is because the output code is exactly the same in different positions. For example, in positions 1,5,9 and 13 as shown in the Truth Table.