These transmission, engine or driveline mounted units harness mechanical power from the vehicle’s running engine to operate many kinds of onboard equipment a technician may use on the jobsite. A PTO may power hydraulic systems in heavy lifting or pulling equipment like cranes, winches and hoists, air compressors used in pneumatic tools, welders, or produce electricity for generators to operate power tools. They are most popular in applications that demand high power output and efficiency.