ABS is short for Anti-lock Brake System. It is made up by five parts：
1. ABS Control Unit（控制单元）
2. ABS Hydraulic Unit（液压模块）
3. Wheel Speed Sensor（轮速传感器）
4. Phonic Ring（音轮）
5. Front/Rear Brake Circuit（前后轮制动回路）
ABS can judge whether the wheel is in slipping or not by observing the speed of wheels. Once there is a lower speed far than another, the ABS Control Unit will control ABS Hydraulic Unit to decrease the oil pressure of the pipe.