Filmstrip was a related series of still pictures on 35-millimeter film. A projector flashed one after another of these pictures on a screen. From about the 1940’s to the 1980’s, teachers used filmstrips for instruction. They were easier to use, could be stored in less space, and cost less than slides.
Filmstrips were black and white or in color. A record player or tape recorder attached to the projector provided sound for some filmstrips. The recording explained the film and sometimes had music and sound effects. Some recordings changed pictures automatically by transmitting a silent signal to a special type of projector. Other types gave a beep when the operator should change pictures. But teachers often preferred to explain the picture themselves or to have a pupil do it. In this way, the picture could be changed whenever desired. Students could ask questions immediately instead of waiting until the end of the picture.