carbon microphone

British  

noun

1. a microphone in which a diaphragm, vibrated by sound waves, applies a varying pressure to a container packed with carbon granules, altering the resistance of the carbon. A current flowing through the carbon is thus modulated at the frequency of the sound waves

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Example Sentences

Mr. Peer, armed with new portable technology — including a type of carbon microphone that made sound recordings considerably truer — traveled to Tennessee to record what he called the area’s “hillbilly music.”

From New York Times • Aug. 19, 2019

A carbon microphone with a dry cell in series was connected to two or three turns of wire wound over the coil.

From The Dawn of Amateur Radio in the U.K. and Greece: a personal view by Joly, Norman F.