Abstract: In a film projector of the type wherein film advance is controlled by pulse signals generated by a tape recorder or the like, a protective filter is automatically inserted into the optical path between the projection lamp and the film when the time interval between successive pulse signals exceeds a predetermined time limit. The filter is automatically removed from the optical path only when two successive time intervals have a duration less than a predetermined duration.

Abstract: A composite projector gate, aperture and light dowser assembly for a cinematograph film projector. The film guide surface through the gate area is curved convex towards the light source, film being held to curved marginal guides by flexible bands anchored before the gate, in the direction of film motion. A quick-release anchor is provided to retain the tension springs. The projection aperture comprises a removable plate in front of which, towards the light source, are spaced-apart heat screens with a horizontally-moving light-dowser blade therebetween in a space in which is provided forced air ventilation.