Abstract: A temperature sensitive control circuit for an electrically heated rotatable drum (11) including an internally disposed electric heater (27) and an electric temperature sensor (28) and, outside of the drum, an electric supply (30) for heating the heater and a D.C. supply (31) for producing a constant electric current through the sensor, wherein the electric connections with the drum occur through two sliding contacts (89, 90) only and a diode (29) bypasses the voltage of the heating supply around the temperature sensor. The heater current supply and the sensor current supply operate alternatively and the sensor measures drum temperature while the heater current is interrupted.