Morse's telegraph. Historical artwork of the transmitter of a telegraph machine used to send Morse code. The operator tapped out the code on the button at upper left. Morse code represents each letter and number by a series of dots and dashes. By holding down the button for varying lengths of time, a short or long electrical signal was sent down the wire. A receiver at the end of the wire then converted these signals into a print-out of dots and dashes, which could be translated back into the message. Morse sent the first telegraph message in 1844. For an image of the receiver, see image V400/069.