Supply PowerMaster model "MG" Industrial Duty Hoist type operator rated for use on Sectional Doors with High Lift or Vertical Lift and Rolling Service Doors and Grilles . Primary speed reduction shall be by means of an industrial gear box with bronze worm gear in an oil bath. Motor shall be of the high starting torque, continuous duty industrial type, protected from overload by a current sensing or thermal type overload device. Motor controller shall be a heavy duty, full voltage, across the line, magnetic reversing contactor, that is mechanically and electrically interlocked.