Product Details: Update your semi with enhanced protection of its auxiliary equipment, with the Chelsea Power Take-Off Electronic Over Speed Control Box that ensures you're Ready for the Road Ahead™. Due to its advanced circuitry, this replacement PTO accessory is able to sense the vehicle speed from the PTO drive gears, rather than the alternator. Constructed with an auto re-engage feature for enhanced control and reliability. FleetPride is your First Click in Heavy Duty®.