Abstract: An electronic digital linear shaft encoder which is totally self-contained and readily adaptable to a variety of different equipment using different mounting configurations is disclosed. This encoder mechanism provides an accurate, reliable alignment system within the self-contained unit for aligning a transparent, coded, dimension measuring grid within a photooptical system for assuring that, regardless of the alignment of the equipment being measured or the alignment of the self-contained encoder unit on this equipment, proper alignment will be maintained between the measurement grid and the photooptical system to avoid erroneous output signals and thereby assure reliable performance of the encoder unit.