There are two systems for powering handpieces: air turbine and electrical. Air driven handpieces contain an air-driven spinning turbine to generate rotation, and are powered by compressed air. They can reach speeds of up to 400,000 rpm with a variable torque. Electric motor handpieces use an electric motor to drive the head and can be considered self-contained systems. Internal gearings allow them to run at a constant torque (consistent power) with speeds of up to 200,000 rpm. Electric handpieces are quieter and don't produce the same vibratory sensation.