The housing of a motion-picture camera has a cassette- receiving space into which at least one feeler projects to detect the insertion of a sound- film cassette differing in shape from a silent-film cassette. With both types of cassettes the film is intermittently transported past an image gate by a traction claw; in the case of a sound- film cassette a portion of the film downstream of the image window is accessible for engagement by a constant- speed feeder in the vicinity of a sound- recording head. The feed rate of the traction claw is stabilized by a centrifugal governor in the presence of a silent-film cassette; upon sensing a sound-film cassette, the feeler deactivates the governor and synchronizes the claw drive with the constant-speed feeder under the control of a mechanism, such as a loop detector, which measures the length of film between the image gate and the recording head.
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