Telephone is a device that is used to transmit the sound at long distances from its source. In the world there are approximately 400 millions telephones used in the world. The telephones used today are almost the same form as were patented by Graham Bell in 1876 to 1877. Handsets and the telephones used world wide are almost the same.
In a telephone sound waves are converted into the electrical oscellitations (slightly swinging) and then again turned into the sound waves when reach to the receiver.This oscellitation can travel 900,000 times faster than the sound waves. In the mouth piece of a telephone set, there is small transmitter that transmits the sound, produced by the speaker, into vibrating air molecules, generated through speech, that creates the vibration into the electrical diaphragm (disc that creates sound).This vibreation is transmitted into a piston that is a metallic box filled with granules of carbon. Sound waves are again converted into electrical signals which are converted back to the sound waves at the ear piece.