Abstract: A drive for a slide projector utilizing circular magazines which permits the slide projector to be used with circular magazines having differing numbers of slide compartments. A variable gear unit, including a shift mechanism to vary the gear ratio, couples a drive motor to a drive ring for rotation of a circular magazine disposed in the projector. The circular magazine is rotated in a stepwise manner, the length of each step depending upon the number of slide compartments which the particular magazine contains. The drive ring is made sufficiently large to accommodate most conventional circular magazines and includes a cam which extends radially inwardly and which is adapted to engage a notch formed on the outer surface of a circular magazine. The circumferential step length is adjusted by changing the gear ratio in the variable gear unit by longitudinal movement of an intermediate drive shaft.