Understanding Morse code
A binary language, on a wire.
The first global digital protocol — built before the word "digital" had a meaning.
What Morse is.
Morse code is a variable-length encoding of the Latin alphabet and digits using two symbols — a short pulse (dit) and a long pulse (dah). A short gap separates symbols inside a letter, a longer gap separates letters, and a longer one still separates words. The receiver decodes by listening to gaps as much as to pulses.
SOS = ··· — — — ···
Why E is one dit.
Samuel Morse and Alfred Vail studied the type cases of a Massachusetts newspaper office in the 1830s — the more often a letter appeared in print, the more compartments held a copy. They assigned the shortest signals to the most common letters. E, the most frequent letter in English, became a single dit. T became a single dah. Q, used rarely, ended up four symbols long. The encoding is, in spirit, a hand-tuned Huffman code decades before Huffman.
A worked encoding.
The word HELLO becomes ···· · ·-·· ·-·· ---. Read each letter, separate letters with a wider pause, and the message reassembles itself. HELLO WORLD takes one extra-long pause between the two words.
HELLO in Morse
H = ···· E = · L = ·-·· O = ---
Letters separated by short pauses; words by long ones.
HELLO → ···· · ·-·· ·-·· ---
= ···· · ·-·· ·-·· ---
SOS isn't an acronym.
The international distress signal is ··· --- ··· — three dits, three dahs, three dits — chosen because it's unmistakable on a noisy channel. The "Save Our Souls" reading came later as a memory aid; the signal itself is just a uniquely recognisable rhythm that won't be confused with normal traffic.
What replaced it, and what didn't.
Maritime services dropped Morse as a required protocol in 1999; the U.S. Coast Guard had stopped monitoring 500 kHz a few years earlier. Aviation never used it for general traffic but still identifies VOR navigation beacons with two- or three-letter Morse. Amateur radio kept it because it punches through noise when voice and even digital modes don't — a five-watt CW transmitter and a careful operator can cross continents.
Why it still teaches you something.
Morse is a clean illustration of the trade-off between code length and probability. Common things deserve short labels; rare things tolerate long ones. The same insight underlies ZIP, JPEG, audio codecs and every other modern compression scheme — variable-length codes for symbols whose frequencies you can estimate in advance.
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