Abstract: A device for providing an indication of the position of a material (80) within a conveyor system includes a dancer roller (83) for engaging the material (80) and bidirectionally varying its angular position relative to a preselected axis, and a transducer (10) operatively connected via a shaft (15) to the dancer roller (83). Transducer (10) includes a plurality of light emitting diodes (21,22) and phototransistors (23,24) mounted in spatial relation upon a plate (33) perpendicularly fixed to the shaft (15) and adjustably carrying a plurality of light cams (34,35) interposed between the light emitting diodes (21,22) and the phototransistors (23,24). As the angular position of shaft (15) is varied by dancer roller (83), illumination upon phototransistors (23,24) similarly proportionally varies.