Abstract: A data printer prints alphanumeric information on photographic slide mounts. The data printer includes a platform and a pair of parallel guide rails which define a slide track along which slide mounts are advanced. The platform has a printing aperture through which a print head prints alphanumeric characters onto a bottom surface of the slide mount positioned at the printing station. A pair of generally parallel conveyor belts are positioned above the platform and extend along the slide track so that a slide mount at the print station is held between the lower runs of the belt and the platform. A DC electric motor is connected to the conveyor belts through a pulley, and performs two functions: slide mount motion sensing during each cycle and slide mount ejecting at the end of each customer order. The motion sensing function is provided due to the movement of the belts as the slide mount is pushed into the printing station by a subsequent slide mount.