American Morse code

How to read it

Britannica says Morse invented his code in the 1830s for the electric telegraph and his assistant and partner Alfred Vail improved it. In Europe it lacked codes for letters with diacritic marks, so a conference of European nations devised the International, or Continental, Morse Code in 1851. The International code uses dots and short dashes for every letter, with dashes of one constant length; the original used patterns of dots and spaces for a few letters, and dashes of varying length. Thomas H. White’s history of early radio names the long dash for L and the internal spaces within some other letters. The American telegraph industry kept the original code until teleprinters spread in the 1920s and ’30s, according to Britannica.

Also searched as: american morse vs international morse, continental morse, landline morse, morse vail code, original morse code, railroad morse code.

How the two codes differ

Many characters are the same in both: three dots are S in either code. Others are not. White notes that three dashes are O in Continental Morse and the figure 5 in American Morse, and ARRL’s glossary says the zero in landline Morse is a long dash. White adds that the rhythm of the two codes was different enough for an operator to tell them apart, and that with practice some operators could send and receive both.

Paper tape, then clicks

The Library of Congress describes Morse’s first system: a sender with long and short metal bars for the letters and numbers, and a receiver whose stylus dented a paper tape for the operator to read. As lines spread, operators took to reading the code by ear in real time. ARRL says landline operators listened to the clicks of a sounder, not to tones. Morse’s famous message, “What hath God wrought?”, went from Washington to Baltimore on 24 May 1844; ITU-R M.1677-1 dates versions of the code from 1844.

Which code radio took

The 1906 Berlin convention’s service regulations say the signals to be employed are those of the Morse International Code. The US Navy switched to Continental Morse for radio; White quotes H. N. Manney, chief of the Bureau of Equipment, writing in 1905 that “Experts in two codes are rare”. Continental Morse became the world radiotelegraph standard and was renamed International Morse, while American Morse mostly left radio but stayed the standard on US land telegraphs. It is why the distress signal was read “S 5 S” on the Great Lakes in 1912: see SOS in Morse code. The International alphabet is on Morse code alphabet.