1-155-352 - Ann Ronan Picture Library/Heritage-Images

Carbon microphone, invented in 1878 by David Edward Hughes, 1890. The apparatus was said to be so sensitive that a fly walking on the sounding-board could be heard by an observer on a telephone several miles away. From Electricity in the Service of Man translated by R Wormell from the German of Alfred von Urbanitzky. (London, 1890).