Telephone:
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 a microphone strung together with wires (a cup 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.