Samuel Morse invented a machine to send messages over long distances. This machine, called a telegraph, uses an electromagnet to send electricity through a wire. Pressing a key on the telegraph interrupts the flow of electricity and creates a pulse.

Morse developed a code using pulses of different lengths, some short and some long. A different pattern of short and long pulses represents each letter of the alphabet, numbers, and punctuation. This electric alphabet became known as Morse code.