Abstract: Disclosed herein is an arm deflecting drive system for strip chart recorders. The drive system mechanism includes a variable resistance structure which produces a position signal indicative of the angular position of the deflecting arm, which signal is proportional to the tangent of the position angle of the arm. The drive mechanism further includes a differential amplifier receiving both the position signal and a reference signal and generating a deflection signal related to the difference between the reference and position signals. In accordance with the invention, the variable resistance structure may include a track of electrically resistant material contoured to provide the tangential relationship between the position signal and the position angle or, alternatively, the track may be formed from an inhomogeneous material to provide such tangential relationship.