Abstract: The present disclosure involves a rotational encoder having a plurality of indicia at fixed positions with respect to each other, means for rotating said indicia about an axis and means for sensing the indicia positioned along the path of rotation of said indicia. In the present apparatus, each of a plurality of said indicia has a first edge radial to said axis and traversing the path of rotation and a second edge nonradial to the axis also traversing the path of rotation and the apparatus further includes means for moving the sensing means so that the position of the sensing means may be adjusted with respect to the first edges which are the leading edges when said indicia are rotated in one direction and to the second edges which are the leading edges when the indicia are rotated in the opposite direction.