The telephone was invented in 1876 by Alexander Graham Bell and revolutionized human communication, making it possible to transmit voice over distances.
Prior to this, people relied on letters or messengers to communicate with those far away. Bell's first telephone consisted of a receiver and a transmitter connected by a wire.
When someone spoke into the transmitter, the voice vibration was converted into an electrical signal that was transmitted through the wire and then converted back into sound by the receiver.