There are two rings of alternating back and white areas. The inner ring is the ‘A’ ring, and the outer ring is the ‘B’ ring. Each ring has a sensor that returns a ‘1’ when faced with white, and a ‘0’ when faced with back. These sensors output two pulse trains, normally called ‘A’ and ‘B’ as per the ring.
The image below shows the disk for a quadrature encoder. This device creates a series of pulse strings when a shaft rotates, and is…