Abstract: A lever mechanism having an output end and an input end wherein the input end is pivotally mounted to a fixed support and provided with a track portion. The track portion has a spaced apart relationship to the pivot axis of the lever and is provided with a generally V-shaped portion and lateral side portions oppositely extending therefrom. A reference force is applied through a roller member which is positioned along the track by a variable input position signal applied thereto. The apex of the V-shaped portion is on a line through the pivot axis such that with the roller member held in a bottomed position and engaging both sides of the V-shaped portion there is no input moment applied to the lever mechanism and movement of the roller member in either direction from a null position produces a clockwise or counterclockwise motion of the output end of the lever mechanism, depending upon the direction of movement of the output end in response to the roller movement.