film, the music overlaps the opening notes of the next, so that with proper operation the audience is unaware of any change being made.

In ordinary moving picture projection, the film is usually shown at a faster speed than It was taken. However, this cannot be done with a synchronized film or a sound film, as the pitch would be changed and this would cause the voice or music to be distorted and spoiled. All synchronous subjects have therefore to be shown at exactly the same speed they were made, which is 90 ft. per minute. This speed is maintained automatically by means of a special type of motor and an electrical governing system contained in the motor control box. (Fig. 2)

To permit of running films other than synchronized numbers in the usual manner, means are provided on the motor control box for regulating the speed within the usual range employed in projection.