A brief history of the Morse code

££) In the early nineteenth century, all of the essential components necessary to construct an electrical communication system had been discovered. The most important of these were the battery by Volta, the relationship between electric current and magnetism by Oersted, and the electromagnet by Henry. It now remained for someone to find a practical method to combine these technologies into a working communication system.

££)Some commercial electrical communications systems existed in Europe as early as the 1830s. A classic example of this is the English ‘Needle Telegraph’. The needle telegraph required two or more lines to form a complete circuit. It was relatively slow and the design of the transmitting and receiving instruments was complex. Something simple and efficient was needed.

££)The Morse system of telegraphy was invented by Samuel Finley Breese Morse (an American painter and founder of the National Academy of Design in New York) in the 1840s in the United States. Morse code is essentially a simple way to represent the letters of the alphabet using patterns of long and short pulses. A unique pattern is assigned to each character of the alphabet, as well as to the ten numerals. An operator using a telegraph key translates these long and short pulses into electrical signals, and a skilled operator, at the distant receiving instrument, translates the electrical signals back into the alphabetic characters. This was demonstrated in 1844 sending the message ‘what hath God wrought’ via an experimental telegraph from Washington DC to Baltimore.

££)In the 1920s automated teleprinter technology had become reliable enough to begin to replace the Morse operator. Manual landline telegraphy was slowly phased out until the 1960s when Western Union and the railroads discontinued use of their last Morse circuits. Morse continued to be used in Canada until the mid-1970s, and railroads in Mexico were still using the wire at least until 1990. A small but hardy group of retired telegraphers and telegraph enthusiasts continues to keep landline Morse alive in the US via a mode called ‘dial-up’ telegraphy.

££)A dot is the basic timing element. A dash is equivalent to three dots. A space between the dots and dashes in a character is equivalent to one dot and the spaces between characters are three dots long. Words are separated by seven dots in length.Note that the most frequently occurring characters have the shortest length and vice versa. This relationship is similar to the relationship between frequency of occurrence of letters and their points value in the game Scrabble.Morse matched the information source (a piece of newspaper text) to the telegraph channel, eliminating some redundancy and efficiently coding the alphabet. This is one of the earliest forms of source coding where the code is matched to the source data. Source coding will be discussed later in the chapter.