Morse code is a method of sending text as a series of short and long signals, called dots and dashes. Each letter and number has its own pattern, and the signals can be sent as sound, light, electrical pulses or radio waves.
How Morse code works
Morse code is a code, not a language. It spells out words letter by letter, in whatever language the sender writes. Each character is a fixed pattern of two signals:
- a dot (also called a "dit"), a short signal
- a dash (a "dah"), three times as long as a dot
The silence matters as much as the sound. A short gap separates the parts of one letter, a longer gap ends a letter, and the longest gap ends a word. Without those gaps, ... could be S, or EEE, or IE. The guide to reading Morse code explains the exact timing.
Because it only needs "on" and "off", Morse code can travel through almost anything: a telegraph wire, a radio, a flashing light, a whistle, or taps on a wall.
Who invented Morse code?
Morse code was developed in the United States in the late 1830s for the electric telegraph. Samuel Morse, a painter turned inventor, worked on the telegraph with the scientist Joseph Henry and the machinist Alfred Vail. Morse's first code, around 1837, sent numbers that stood for words in a codebook. Vail expanded it into a code for individual letters and characters around 1840.
On 24 May 1844, Morse sent the message "What hath God wrought" over a telegraph line from Washington, D.C., to Baltimore, opening the first long-distance telegraph line in the United States.
International vs American Morse code
The code we use today is not quite the one Morse and Vail created.
- American Morse code was the original, used on North American railway and telegraph lines. It had dashes of different lengths and spaces inside some letters, which made it fast for skilled telegraphers but easy to misread.
- International Morse code grew out of a simpler version written by Friedrich Gerke in Germany in 1848. It uses only one length of dot and one of dash. It was standardised at the International Telegraph Conference in Paris in 1865, and is now defined by the International Telecommunication Union in Recommendation ITU-R M.1677-1.
International Morse code is the version used everywhere today, including by this site's translator.
Where Morse code is used today
Morse code is no longer used for everyday messages, but it has not disappeared.
- Amateur radio. Many radio amateurs ("hams") use Morse code, which they call CW. It gets through weak and noisy signals better than voice. In the US, the FCC stopped requiring a Morse code test for amateur licences in February 2007, yet it remains popular.
- Aviation. Radio navigation beacons identify themselves with a few letters in slow Morse code, so pilots can check they are tuned to the right station.
- Accessibility. Some people with limited movement type using Morse code with one or two switches, a sip-and-puff device or eye blinks. Android supports Morse code input on its keyboard.
- Emergencies and survival. SOS can be sent with a torch, a whistle or by tapping when nothing else works. See SOS in Morse code.
- Puzzles, games and gifts. Hidden Morse messages appear in escape rooms, video games, jewellery and films.
The end of Morse code at sea
For most of the 20th century, ships kept radio operators listening for Morse code distress calls. The Global Maritime Distress and Safety System (GMDSS), using satellites and automated alerts, replaced Morse code for maritime distress in 1999.
Quick facts
| Question | Answer |
|---|---|
| Shortest letter | E, a single dot . |
| Longest standard codes | Numbers and most punctuation, 5–6 signals |
| Speed unit | Words per minute (WPM), based on the word PARIS |
| Standard | ITU-R M.1677-1 |
| Newest character | @, added in 2004 |
| Best-known message | SOS, ...---... |
Sources: Morse code on Wikipedia, ITU-R M.1677-1, ARRL bulletin on the end of Morse testing.