Abstract: Opaque/translucent-transparent markings on a flat track pass through a gap defined by a carrier body sealed in a casing and having peripheral grooves ending at the gap of the body for embedding light conductors connected to light emitting and receiving means aranged generally on opposite sides of the gap.

Abstract: The present invention relates to the digital control of a machine or equipment, particularly but not exclusively a matrix printer under utilization of an increment step sensor monitor or pick up operating on the basis of optic electronic principles and including at least one source of radiation and at least two pickup transducers disposed in the ray path from the source of illumination and further including a marker track composed of alternating transparent or translucent and opaque increments being unilinearly moveable, either on a curved or on a straight path.