A Code Designed Around How Often You Type
Morse code encodes text as sequences of just two signal lengths — dots and dashes, or dits and dahs. That is the entire alphabet: two symbols and the silence between them.
The clever part is the assignment. Alfred Vail, the engineer working with Samuel Morse, designed the original alphabetic code so that each symbol's duration was roughly the inverse of how often its character appears in English. Common letters got short codes; rare ones got long codes. This is why E, the most common letter in English, is a single dit.
That idea — spend the fewest symbols on the most frequent thing — is the same principle behind modern data compression, invented a century early by someone trying to save time on a telegraph wire. Morse's own preliminary proposal was actually replaced by Vail's alphabet-based version, and Friedrich Gerke later simplified Vail's code to produce the version adopted in Europe. Most of the alphabetic part of today's ITU standard comes from Gerke.
Everything Is Measured in Dits
Morse timing is proportional rather than fixed, which is what makes it work across wildly different speeds and mediums.
Once a rhythm is established, the dit becomes the basic unit of time. From there everything follows:
- A dah lasts three times a dit
- Each dit or dah inside a character is followed by a space equal to one dit
- Letters are separated by a space of three dits
- Words are separated by a space of seven dits
Because the code is defined by proportion, it is usually sent at the highest rate the receiver can decode. The ITU International Morse code covers the 26 basic Latin letters, the accented É, the numerals 0 to 9, plus punctuation and procedural signals called prosigns. There is no distinction between upper and lower case — a detail that seems trivial until you realise it halves the alphabet you need to memorise.
Seventy-Five Words a Minute, Set in 1939
Skilled operators reached speeds that sound impossible for a two-symbol code tapped by hand.
Theodore Roosevelt McElroy set a record of 75.2 words per minute in 1939 — and it still stands. Some operators are believed to have exceeded 100 WPM, at which point they are no longer decoding individual letters but hearing whole phrases as sound shapes, the way you read words rather than letters.
Measuring the speed needs a convention, since word lengths vary. Two standard words are used: PARIS, which occupies 50 dit units, and CODEX, which occupies 60. Because they differ, the same operator can be reported at speeds varying by up to 20% depending on which standard is quoted. Commercial radiotelegraph operator licences have required proficiency of 20 WPM for plain text and 16 WPM for code groups — random letters, which are far harder because you cannot guess ahead.
The Last Message Was the First Message
Morse telegraphy opened with a line chosen for weight. Samuel Morse's inaugural commercial transmission in 1844 was the biblical phrase "What hath God wrought."
It closed the same way. On 12 July 1999, the era of US commercial Morse ended when operators signed off by sending Morse's original 1844 message, followed by the prosign SK — end of contact.
The maritime world let go around the same time. The Global Maritime Distress and Safety System replaced Morse as the international maritime standard in 1999, and the French Navy sent its final transmission on 31 January 1997 with a line that reads like an epitaph: "Calling all. This is our last call before our eternal silence." Amateur radio held on longer, until the 2003 World Radiocommunication Conference made Morse proficiency optional for licensing, ending a requirement that had been effectively universal for decades.
Still Blinking, Still Beeping
Morse survives because it needs almost nothing. It can be sent through electric current, radio waves, visible light or sound — anything that can be switched on and off. It can be memorised and perceived directly by a trained human, with no equipment at all in the receiving chain.
That property produced one of the twentieth century's most extraordinary messages. During the Vietnam War, prisoner of war Jeremiah Denton was filmed for a televised broadcast — and blinked TORTURE in Morse to American observers watching, reporting his treatment past his captors without saying a word.
It is also still quietly in service. Pilots identify radio navigation aids by call signs of two to five letters transmitted in Morse, printed on aeronautical charts so a crew can confirm they are tuned to the station they think they are. A code designed in the 1830s for copper wire is still being decoded by ear in cockpits today.
