Abstract: Method and apparatus for increasing the efficiency and safety of conducting heat treating operations with conventional welding equipment by eliminating mechanically-operated contacters. The apparatus operates on low power and produces low power level signals and controls power sources capable of producing high power levels for both welding operations and powering a heating element for heat treatment. The signal produced by the apparatus reflects a difference between an operator-selected desired temperature and the actual temperature of the workpiece and is current limited to a level proportional to the operator-selected desired power level of the welding power source to control the rate at which the heating element connected thereto heats the workpiece.