ATB stands for automatic torque biasing, which means the LSD unit is constantly diverting torque between the two front wheels at all time.
Made from CNC billet steel, the LSD unit is maintenance free and they backed it up with a life time warranty. Yup, no kidding.
If you so happen to be able to break it, just send the unit back to Quaife and they will replace it with another one no questions asked.
Click here if you want to find out more about it, meanwhile here are some pictures of the LSD unit for your viewing pleasure.