The word "microphone" comes from the Greek words "micro", meaning "small", and "phone" meaning "voice". It first appeared in a dictionary in 1683 as "an instrument by which small sounds are intensified".This was in reference to acoustical hearing devices such as the ear trumpets and megaphones of that era.
Microphones as we know them started with the first articulate telephone transmitter,developed almost simultaneously by Elisha Gray and Alexander Graham Bell.This was the liquid transmitter of 1876.This transmitter would be classified as a variable-resistance device.Its operation was as follows: the user talked into the black funnel-shaped mouthpiece,at the base of which is a stretched membrane diaphragm.A metal pin through the center of the diaphragm extends down into the metal cup below. The cup contains a dilute acid.An ohmmeter between the cup and the pin will show a fixed resistance. Any movement of the diaphragm will move the pin up and down in the liquid and the resistance will vary accordingly.If wires from the pin and cup were connected in series with a battery and telephone receiver,any talk directed into the mouthpiece would produce articulate speech in the receiver.