There are two Morse codes. American Morse, also called Railroad Morse, is the original code from the 1840s, used on telegraph wires in North America; it has dashes of three different lengths and gaps inside some letters. International Morse is the simpler code adopted in 1865, with one dash length and no gaps inside letters. International Morse is the one used on radio, in aviation and on this website.
Most of the time, when people say "Morse code" today, they mean International Morse.
Where the two codes came from
Samuel Morse and Alfred Vail developed their code in the late 1830s and early 1840s for the American telegraph. That code kept its place on North American landlines and railways for more than a century, which is why it is called Railroad Morse.
In 1848 Friedrich Gerke simplified it for the German telegraph. His version was adopted in Germany and Austria in 1851, and in 1865 an international conference adopted a code based mostly on Gerke's. That became International Morse code, now defined by the International Telecommunication Union in Recommendation ITU-R M.1677-1. The full history is in a short history of Morse code.
What makes American Morse different
International Morse uses two kinds of sound and three kinds of silence: the dot, the dash, and the gaps between signs, letters and words. American Morse uses more:
- A long dash for the letter L.
- An even longer dash for the number 0.
- A gap inside the letter, longer than the normal gap between signs, in C, O, R, Y, Z and the ampersand.
So the American O is not three dashes. It is a dot, a pause, and another dot. To an untrained ear that sounds exactly like the two letters E E, and American telegraphers had to learn to hear the difference in the length of the pause. The same goes for C (two dots, a pause, a dot) and R (a dot, a pause, two dots).
Letter by letter
Many letters are the same in both codes: A, B, D, E, G, H, I, N, S, T, U, V and W among them. Others differ completely. A few examples:
| Letter | International | American |
|---|---|---|
| C | -.-. |
dot dot, pause, dot |
| F | ..-. |
dot dash dot |
| J | .--- |
dash dot dash dot |
| L | .-.. |
one long dash |
| O | --- |
dot, pause, dot |
| P | .--. |
five dots |
| Q | --.- |
dot dot dash dot |
| R | .-. |
dot, pause, dot dot |
| 0 | ----- |
one very long dash |
Look at how they cross over. The American F is the International R. The American J is the International C. The American P, five dots, is the International number 5, ....., and the American Q is the International F. An operator trained on one code would misread a message in the other. Tap the International codes in the table to hear them.
Why the world chose the simpler code
On land wires, American Morse worked well, and it was faster: with fewer dashes, it could be sent about 5 percent faster than International Morse, which is partly why Western Union kept using it. But two of its features caused trouble:
- On long cables, closely spaced signals blur together. The first transatlantic cable of 1858 could carry less than one word a minute. American Morse, with its many closely spaced dots, suffered more from this than Gerke's code did, so Gerke's code was adopted as the standard for cables in central Europe.
- The internal pause is easy to mistake. A pause inside a letter that is only a little longer than a normal gap is fragile, especially through noise or when a tired operator's timing drifts.
On radio the problems got worse, because signals fade, crackle and overlap. International Morse, with only one dash and no hidden pauses, is far more robust. Apart from some domestic traffic in North America, on the Great Lakes and along the coasts, radio used International Morse, and it still does.
Is American Morse still used?
Hardly. It lasted on North American railways and landline telegraphs well into the twentieth century, and retired telegraphers long kept using it on the amateur bands, but today it is nearly extinct. Everywhere else, including amateur radio and aviation, International Morse is the standard.
Which one does MorseBeep use?
International Morse, exactly as the ITU defines it, for every letter, number and punctuation mark. The alphabet chart lists them all, and how Morse code works explains the timing. If you are working from an old railroad document, keep the table above at hand: a "five dots" in American Morse is a P, not a 5.