(1995) A US Navy Seaman uses a light to signal in Morse code.
Post Office Engineers inspect Marconi’s equipment on Flat Holm, May 1897
Guglielmo Marconi and George Kemp, 1901. A Morse Inker is seen in the foreground.
A J-38 telegraph key. Mass manufactured in the US during WW2
International Morse Code encodes the ISO Basic Latin Alphabet
Morse code is a method of transmitting text information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment. The International Morse Code encodes the ISO basic Latin alphabet, some extra Latin letters, the Arabic numerals and a small set of punctuation and procedural signals (prosigns) as standardized sequences of short and long signals called “dots” and “dashes”, or “dits” and “dahs”, as in amateur radio practice. Because many non-English natural languages use more than the 26 Roman letters, extensions to the Morse alphabet exist for those languages.
Each Morse code symbol represents either a text character (letter or numeral) or a prosign and is represented by a unique sequence of dots and dashes. The duration of a dash is three times the duration of a dot. Each dot or dash is followed by a short silence, equal to the dot duration. The letters of a word are separated by a space equal to three dots (one dash), and the words are separated by a space equal to seven dots. The dot duration is the basic unit of time measurement in code transmission. To increase the speed of the communication, the code was designed so that the length of each character in Morse varies approximately inversely to its frequency of occurrence in English. Thus the most common letter in English, the letter “E”, has the shortest code, a single dot.
The signal of SOS – referred to in morse code by three dots, followed by three dashes, followed by three dots (. . . – – – . . .) was selected as the universal distress signal due to it being extremely easy to transmit and stremely easy to recognise.
Several mnemnonic devices have come about to help sailors rememnber this sequence – including Save Our Ship, Save Our Souls, and Send Out Succor. But none of these acronyms are the origin of this sequence.
Germany introduced the SOS signal on April 01, 1905, and by 1908 it had become the universally accepted signal for a ship in distress. The first ever recorded SOS transmission was by RMS Slavonia, sent out on June 10 1909, and the signal remained the international standard maritime distress signal until 1999, when it was replaced by the Global Maritime Distress Safety System – which combines satellite, terrestrial and ship-board radio systems. The last significant international use of the SOS signal ended on February 1, 1999