Trigger Switch With Lock-On Button (AC).SJS (Super Joint System) prevents kickback during wheel lock up for optimal tool and operator protection. Electronic current limiter prevents motor burnout due to overloading. Soft start feature gradually increases speed to eliminate start up shock. Constant speed control maintains constant speed under heavy load. Anti-Restart feature prevents accidental start up of tool if switch is locked in the on position. LED Light indicates active power supply and activation of anti-restart feature. Labyrinth construction features a complex series of channels to prevent penetration of dust and debris into the field and armature for maximum operational life.