Abstract: A digital rotary shaft position encoder includes a disk having a plurality of digitally encoded apertured tracks. The successive binary characters read from the tracks each have at least one 1 and comprise a repeating code having a different order of characters when read in one direction than when read in the other. The code is sensed to determine the direction of rotation of the shaft. The at least one 1 in each character is sensed to produce a clock pulse and these are counted to provide position information. The count is incremented or decremented in accordance with the direction information.