A telegram is a message sent through electrical signals fed through a wire. Most telegrams use Morse code to transmit and receive signals through the wire.
The invention of electricity led to new ways of sending messages over long distances. The first electric telegraphs were sent with devices consisting of wires and receivers. They relied on electric charges through the wires, and receivers such as clocks and burn marks in paper showed the messages on the other end. In 1837, an American inventor named Samuel Morse invented and patented a machine that used a specific code of long and short signals to encode the alphabet. His machine sent these signals as long and short electric charges, much as earlier machines did. This system was widely adopted worldwide and became a popular method of sending messages.