To this day there have been many different claims on who developed the telephone. Both Alexander Bell and Elisha Gary were working on a phone at that same time. Bell managed to get the to the patent office a few hours before Gary and thus was able to file first. Bell was actually working on the problem of how to send more than one message at a time on the telegraph. Bell was working on the idea of sending different frequencies at that same time.
Bell created the first telephone by created a crude microphone which was a piece of parchment over a cone. When the parchment vibrated it moved an attached needled that was in a pool of diluted sulphuric acid as the vibrations changed it moved the needle that would then vary the current being carried between contacts. That current then traveled along a wire to a another point where the reverse would take place.