Absolute rotary encoders divide into single-turn absolute encoder and multi-turn absolute encoder. The code track is designed by using Gray code, matrix code, cursor code, pseudo-random code, etc. When the shaft rotates, there is a code output corresponding to the position. From the change in code size, the position of the forward and backward directions and the displacement can be distinguish without direction judgment circuit. It has an absolute zero code. When power is outage or turned off, when it is turned on and re-measured, the code of the power outage or shut down position can still be accurately read, and the zero code can be accurately found. ROUNDSS Absolute rotary encoder provide multiple interfaces:RS485, RS422, RS232, SSI, MODBUS, Canopen, parallel or analogue. The sensor has multiple shaft diameters are optional.