The Invention of the tape/slide synchronizer in the 1980's added another dimension to audio-tape instruction: the synchronization of slide projection with audio tape recordings. It works like this:

-An instructor wishes to inform students about how tomake a chair.

-While making one chair, the instructor photographs each part of the process.

-The instructor makes an audio tape explaining each part of the process.

-The slides are organized into a slide tray on a projector which is connected to the sound/slide synchronizer.

-The audio tape is placed in the synchronizer.

-The tape is played by the instructor, who watches the slides. Whenever a slide is to be projected, the instructor presses a button on the synchronizer and inserts an electronic pulse on the audio tape. At the conclusion of this process the tape is rewound to its starting point and the slide tray is placed at its starting point.