David Edward Hughes' carbon microphone, which was independently developed by him in England and Emile Berliner and Thomas Edison in the US, was the first microphone that enabled proper voice telephony. The 'loose contant' carbon microphone was then referred to as a transmitter. Edison was awarded the patent for device after a long legal battle in mid-1877. Hughes had however demonstrated his working device in the presence of several witnesses some years earlier and is thus credited as the microphone's inventor by several historians.

David Edward Hughes.Pic/YouTube

The carbon microphone contains 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. This allowed a relatively accurate electrical reproduction of the sound signal. The credit of coining the term 'microphone' also goes to David Edward Hughes, who demonstrated the device his apparatus to the Royal Society by magnifying the sound of insects scratching through a sound box and decided not to patent his innovation; instead giving it as a gift to the world, a view that was contrary to Edison's.