Telephone is a kind of remote communication equipment that can send and receive sound. As early as the eighteenth century, the word "telephone" was used in Europe to refer to microphones strung together with wires (cups strung together with wires) The telephone was attributed to Alexander Graham Bell. The principle of early telephone is that sound is a compound vibration in the air, which can be transmitted to solids and to conductive metals through electric pulses. ? Bell applied for the telephone patent in March 1876.
Refer to Baidu Encyclopedia Phone