PURPOSE: To control the rotation of driving motor of a projector by comparing a master code recorded in one track of a tape deck with a slave code provided on the film of a projector, and obtaining a difference signal.

CONSTITUTION: A code for indicating a speed and a position of a tape is recorded in advance in at least one track of tape 3a of a tape deck 3. On the other hand, a projector 1 projects a picture, also has the function for reading out a code for indicating the speed and the position of a film, which is provided on the film end part, and also has the input terminal of a control signal in order to control a driving motor of the inside. A synchronizer 2 inputs a master code mc sent out of the take deck 3 and a slave code sc sent out of the projector 1, and provides a control signal cs corresponding to a difference signal of both of them to the driving motor of the projector 1. In such a way, the operation of a sound system always referred to the main, and the quality of a sound is raised remarkably.