A telegraph uses an electric current to send and receive messages. The sender taps a switch and an electric current is turned on, which travels through a wire to the receiver. The sender then taps a message using Morse code, which indicates specific letters.
The electric current powers a buzzer, indicating a message to the receiver. Some telegraphs are sent to operators and others are sent to printing tape, which allows messages to be read at a later date. Most telegraphs use two electrical wires, which allow the current to complete a full circuit, although some simple models use only one electrical wire and a buried wire.