Carbon transmitter

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1.A telephone transmitter in which a carbon contact is used.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
In the 1870s, his carbon transmitter immensely improved the telephone and the telegraph.
And while Thomas Edison invented the idea of the microphone when he placed the carbon transmitter inside a telephone, it was David Edward Hughes, from Bala, who took the idea a crucial stage further.