Abstract: For variable letter sizes being photographically recorded in a second generation phototypesetter, it is desired to increase generated quantities of light flux produced by the flash lamp operating in conjunction with a font disc where larger letter sizes are thereby imaged upon the photosensitive medium, and conversely, to reduce such flux where smaller characters are to be projected. The disclosed system employs a digital letter size code for controlling the amount of charge inserted into a storage capacitor via a digital to analog converter and multivibrator. When the flash lamp is triggered at the appropriate time to selectively illuminate a given character, the energy associated with the stored charge is employed to energize the lamp.

Abstract: Film transport apparatus for phototypesetters. The apparatus includes upper and lower guide plates supporting pinch and drive rollers, respectively, between which a strip of film is frictionally fed. A pair of hold-down rollers are provided to press the upper guide plate against the lower guide plate to maintain the pinch and drive rollers properly positioned against each other, and also to help keep the apparatus locked together during operation. The upper guide plate is designed to be laterally slidable relative to the lower guide and further is provided with a pair of notches cut into its sides. Accordingly, to load film into the apparatus, it is only necessary to slide the upper guide plate until the hold-down rollers become aligned with the notches at which position the upper guide plate can be lifted up and away from the lower guide plate to separate the pinch and drive rollers for film loading.

Abstract: An optical sensor is positioned at the output of a variable magnification optical system which focuses differing character size images upon a photosensitive medium. A reference voltage, which is a function of the proper exposure for a particular photosensitive medium, is compared with the photosensor voltage. The system automatically tests for the correct light flux before each size change by projecting a reference image through the optical system at the photosensor, such image having a relatively low intensity level, so that no output signal is produced by the above-mentioned comparator. The intensity of the reference image is iteratively increased until such output signal is produced by the comparator, thereby to maintain the light intensity at the last level attained, until a character size change is effected, wherein the comparison process is repeated.