The study of lattice defects quenched into small diameter wires requires the precise control of the specimen at elevated temperatures. The circuit described has heated 0.127 mm diam wires to 350°C from 0°C in 2 msec and held the temperature constant to ±5C° in such media as air, mineral oil, and argon at 6 kilobars pressure. Maximum temperature is limited only by specimen design and environment. With an appropriate analog voltage input, the specimen temperature can be varied in any manner within the limits of maximum heating and cooling rates. Of particular interest is the ability of the circuit to provide a linear quench with time constant as long as desired.