Professor David Hughes invented his microphone in 1878, and described it in a paper to the Royal Society in May of that year. His name was already well known in the communications field, since his development of a successful printing telegraph in the 1850s. He termed this type of transmitter a microphone, and it has retained this name ever since. His microphone experiments stemmed from the discovery that sound could be transmitted by imperfect contact between the broken ends of a piece of wire. An early demonstration of the principle involved three nails laid in light contact with each other, but mercurised carbon eventually proved a better medium. In the course of these experiments, Hughes unwittingly anticipated the coherer transmitters of Branly and Marconi.
The Hughes microphone induced a furious argument between Thomas Edison and Sir William Preece, chief engineer at the GPO. Edison also devised a form of carbon microphone (using lamp-black) in 1878, and on learning of the Hughes microphone, accused Preece of giving Hughes information gleaned when he visited Edison in 1877. Preece, who helped promote the phonograph in Great Britain, and would give considerable help to Marconi on his arrival in the country nearly twenty years later, denied passing any such information to Hughes. As with the electric lamp, Edison had come up contemporaneously and coincidentally with the same idea as another inventor.