Compressed air gramophone

One of the earliest versions was the Auxetophone, designed by the Anglo-Irish engineer Sir Charles Parsons.

[1][2][3] It was capable of producing sufficient volume to broadcast public music performances from the top of the Blackpool Tower, and was said to be loud enough to cause people to vacate the front rows of seats in an auditorium.

[2][5] A pneumatic amplifier was realised by using a sensitive valve, which required little force to operate, to modulate the flow of a stream of compressed air.

The basic principle of the valves used in these devices was to pass the stream of compressed air through two partially overlapping combs.

The sound vibrations to be amplified were applied to one of the combs, causing it to move laterally in relation to the other comb, varying the degree of overlap and so altering the flow of compressed air in sympathy with the sound vibrations.

Illustration of a theater from the rear right of the stage. At the front of the stage a screen hangs down with the projected image of a tuxedoed man holding up a text and performing. In the foreground is a gramophone with two horns. In the background, a large audience is seated at orchestra level and on several balconies. The words "Chronomégaphone" and "Gaumont" appear at both the bottom of the illustration and, in reverse, at the top of the projection screen.
1908 poster advertising Gaumont's sound films, showing a Chronomégaphone