Abstract: The recorder includes a heated stylus which is positioned across a heat-sensitive chart by a servo motor to make the stylus position follow the value of an input signal applied to a servo balancing comparing and driving circuit for the motor. A switching circuit, actuated by the pulse signal output of a pulse generator, interconnects the stylus heater, a capacitor, and a source of capacitor charging energy. The switching circuit alternately charges the capacitor from the source and discharges the capacitor into the stylus heater. This causes the stylus to produce a recorded trace on the chart having an intensity which is substantially independent of the resistance of the stylus heater over a given resistance range.