Morse code
What SOS, CQ, the prosigns and the radio abbreviations mean in Morse code, the full alphabet and figures, and the timing that makes a dot a dot, from the ITU’s own recommendation.
Test yourself: Morse code quiz
Signals and calls 4 symbols
The code 5 symbols
About morse code
Morse code writes letters, figures and punctuation as short and long signals, dots and dashes, that can be sent as sound, as light or as a radio signal switched on and off. ARRL’s glossary calls it CW, another name for international Morse code. The ITU defines the code in Recommendation ITU-R M.1677-1, which notes that versions of it have been in use since 1844 and that it is still used by amateur and amateur-satellite stations, and to a diminishing extent in the mobile and fixed services. Its timing is set in units: a dot is one, a dash three, the gap inside a letter one, between letters three and between words seven.
The pages people look up
The best-known signal is the distress call SOS, three dots, three dashes and three dots, which the 1906 radiotelegraph convention signed in Berlin made the signal for ships in distress. It is printed in the convention as one run-together signal, and the ITU says the conference established SOS as the international maritime distress signal. CQ is the general call to any station. The prosigns, such as AR and SK, are letters run together and sent as one character, and the abbreviations and Q codes include 73, ham radio’s “best regards”, and QTH for location.
The code itself
The alphabet page has the whole ITU table, A to Z and 0 to 9, with the sound of each character as ARRL writes it. The figures, the punctuation signals and the timing rules each have a page.
Two Morse codes
Britannica describes two systems. Samuel Morse’s original code of the 1830s, improved by Alfred Vail and now called American Morse, stayed on US landline telegraphs, where ARRL says operators listened to the clicks of a sounder. The International, or Continental, code was devised by a conference of European nations in 1851 and became the global standard; the 1906 convention named it for radio.
These pages say what each signal means and where its definition comes from. The translator on stringmash.com turns text into Morse and back.
Sources
- Recommendation ITU-R M.1677-1: International Morse code, ITU-R M.1677-1 (10/2009), International Telecommunication Union (ITU-R), Scope; considering a) and b); Annex 1, Part I, §§1.1 and 2
- International Wireless Telegraph Convention and Service Regulations (Berlin, 3 November 1906), Navy Department, Bureau of Equipment; Government Printing Office, Washington, 1907 [N5.2:W74/6], US Navy Department (text transcribed by earlyradiohistory.us), Service Regulations, Articles XV and XVI
- ITU’s maritime journey: Then and now, ITU Hub, June 2022, International Telecommunication Union, Maritime safety milestones
- Morse Code, Encyclopaedia Britannica, revised by the editors, Encyclopaedia Britannica, Introduction and history
- Ham Radio Glossary, ARRL Ham Radio Glossary, ARRL, the national association for Amateur Radio, CW (Morse code); Procedural signal (prosign); Q signals; 73
- Learning Morse Code, ARRL, Licensing, Education & Training, ARRL, the national association for Amateur Radio, Introduction; History of Morse Code
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research