Image: Hughes carbon microphone

Description: Crude carbon microphone invented by David Edward Hughes in 1878. It consists of a carbon rod suspended by its pointed ends vertically between two metal electrodes. Sound vibrations transmitted from the wooden back to the carbon-steel contact causes varying pressure on the carbon granules, causing variation in the carbon's resistance. Edwards found that the device was very sensitive, he was able hear the sound of a fly walking on it, and named it "microphone". Edwards did not invent the microphone but experimented with a wide range of "microphonic" electrical contacts.
Usage Terms: Public domain