and reduce the analog signal to the summing point 66 of the low level preamplifier 68 of the servo amplifier system mounted on servo circuit board 92 preamplifier 68 drives a power amplifier 94 which supplies direct current of reversible polarity to the electromechanical actuator 32 which in the broadest sense comprises a reversible motor to position the actuator in accordance with the input analog voltage on line 64 a feedback position sensor 96 mechanically connected to the reversible motor 32 provides a feedback position signal on line 98 indicative of the existing output position the input analog voltage and the feedback signal are algebraically summed at the summing point 66 to supply an error signal on line 100 the feedback signal from the position sensor is also differentiated with respect to time in a differentiator 102 and the resulting rate signal is presented on line 104 on the summing point 106 of the power amplifier 94 to modify the positional signal at the point the position sensor 96 may be any device that generates an analog voltage proportional to position and may be a simple linear potentiometer connected to a stable reference voltage and functioning as a voltage divider the differentiator 102 is preferably an operational amplifier connected to produce an output signal equal to the time rate of change of the input voltage while the reversible motor 32 may be a conventional low inertia rotary d c motor it is preferable for purposes of the present invention that it takes the form of a linear actuator in which.