Once a staple of the educational classroom, the filmstrip projector is a still frame projector, most often made by DuKane. Individual images were on a spooled roll of 35mm film. An annoying BEEEEP 1kHz? tone from an accompanying audio cassette or 33 RPM LP cued the instructor/projectionist when to advance to the next frame.
For more, see http://obsoleteskills.com/skills/usingafilmstripprojector .
For more, see http://obsoleteskills.com/skills/usingafilmstripprojector .