Photographophone

A photographophone is a device, first developed by Ernst Ruhmer of Berlin, Germany in 1900, used to produce and play back audio recordings.

The process is started by speaking into a microphone, connected to a battery pack, whose modulated electrical output produces corresponding variations in the light of an arc (later an incandescent lamp) that passes through a cylindrical lens slot, which creates lines on the moving sensitive film.

This film, after being taken out of the box and developed, shows a series of perpendicular striations parallel to one another, which are a photographic record of the sound waves created by the telephone transmitter output.

In addition, it was described as "The reproduction of speech by this photographic phonograph is astonishingly clear, and in strength resembles the ennunciation of a good telephone when in ordinary use...

It has the advantage of the ordinary wax-cylindered phonographs in that the reproduction is purer and is free from the unpleasant noises caused by imperfections in the mechanism.