Information on the history of the telephone, including inventors Alexander Graham Bell, Thomas Edison and Elisha Gray.
The first device for transmitting sound was Alexander Graham Bell's telephone. Attempting to improve on the telegraph’s limitation of one message at a time, Bell invented first the harmonic telegraph and then, in 1876, the telephone based upon parallels he drew between multiple messages and multiple notes in a musical chord. Further experimenting led to the discovery that because the resistance of a wire being vibrated by a voice could be varied, he could produce a corresponding varied current by immersing it in a conductive chemical. From this, the ability to transmit distinct sounds by wire was born.
The basic machinery for achieving this, even today, is amazingly simple. A sound is inputted via a microphone that records the variances in air pressure of the sound waves, converts then into electrical energy and sends these down the wire. At the other end these signals are sent to the speaker, which converts them back into sound waves to be heard by the recipient.
Bell was not alone in laying claim to the first speaking machine. Around the same time both Thomas Edison and Elisha Gray were also developing similar technologies and Gray registered his patent only one hour after Bell. Gray also was heavily involved with the creation of the harmonic telegraph, one of the first electronic musical instruments.