Carbon arc lamps attached to telharmonium, New York 1907
Capacitor, coil, carbons, keyboard

An oscillating circuit is switched in parallel with a carbon arc lamp, the frequency being controlled via a keyboard. Unsuppressed, the arc continuously produces oscillations within the human auditory range, thus becoming a “loudspeaker without membrane”; the telharmonium was also used as a controlling device around 1907.

 
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