Mahogany coarse carbon granule microphone No. 3, part of Oliver Lodge’s microphone amplifier or relay, 1898 (British patent 9712 of 1898), a precursor of the moving-coil loudspeaker Mahogany coarse carbon granule microphone No. 3
Experimental microphone in sound box, consisting of two small blocks of wood-charcoal pressed upon each other by a spring, probably made by David Hughes, England, 1878-1890 Experimental microphone in sound box, 1878-1890 1878-1890