Microphone

— An electrical device for intensifying sound by the use of a loose carbon contact between two conductors in the circuit of a telephone receiver. Modern carbon telephone transmitters embody this principle, and are e entially microphones. One form of microphone consists of a pencil of battery carbon, sharpened at both ends, and loosely attached in sockets hollowed in two carbon blocks, which form the electrodes of the instrument. The whole, mounted on a resonant sounding board, is extremely sensitive to minute sounds, being literally, as its name indicates, to small sounds what the microscope is to small objects.