Carbon microphone
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
Carbon microphone
Hughes' device used loosely packed carbon granules - the varying pressure exerted on the granules by the diaphragm from the acoustic waves caused the resistance of the carbon to vary proportionally, allowing a relatively accurate electrical reproduction of the sound signal. Hughes also coined the word microphone. He demonstrated his apparatus to the Royal Society by magnifying the sound of insects scratching through a sound box. Contrary to Edison, Hughes decided not to take out a patent; instead, he made his invention a gift to the world.