Telegraph was an important means of communication from the mid-1800's to the mid-1900's. The telegraph was the first instrument used to send messages by means of wires and electric current. Telegraph operators sent signals using a device that interrupted the flow of electric current along a wire. They used shorter and longer bursts of current, with spaces in between, to represent the letters of the message in what became known as Morse code. A device at the receiving end converted the signals to a series of clicks that a telegraph operator or a mechanical printer translated into words. The message was called a telegram if it was sent over wires stretched across land and a cablegram, or simply a cable, if it was sent through cables laid underwater.