In spring 1987 Sumitomo Electric Ind. Ltd.(SEI) started production of an electronic antilock system for a Japanese car manufacturer. Features of this system are: 1. Extremely reliable due to - separate hydraulic control circuit. - dual electronic circuit. - self diagnostic function. 2. Improved pedal feel by using cut-off valves. 3. Easy addition of traction control system. This paper contains the basic concepts and details the components that make up the system.