Electromagnetic retarder is an auxiliary brake mechanism that makes use of eddy current dynamometer theory to produce resistant torque, consuming the kinetic energy before the brake system works, thus enhance easement and security of car driving. 1) Main parts: interface bracket, rotor, stator, coil, joint flange. 2) Five shifts of brake effect. 3) Bear 30%-80% braking, prevent vehicle running aside, brake overheating and tire bursting. 4) Mounting: on the gearbox, axle or in the driving shaft. 5) Maintenance cost reduced by 5-8 times. 6) Independent auto control and manual operation. 7) Application: medium/heavy trucks and passenger cars. 8) Series - B,G series.