These early microphones consist of wood-charcoal blocks in contact and were designed by David Hughes (1831-1900). Hughes was born in England but grew up in the United States where he was a music profesor. In 1878 he invented the first carbon microphones. He discovered that loose electrical contacts are very sensitive to vibrations, including sound. By putting them in a circuit with a battery and a telephone receiver he found that sounds in the receiver echoed the vibrations upon the diaphragm of the telephone mouthpiece.
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