Morse code: letters, numbers and timing
1The lesson in plain words
Morse code turns letters into short and long signals. The rhythm matters as much as the symbols: dot 1, dash 3, gaps of 1, 3 and 7.
Dots and dashes
Morse code writes each letter and figure as a pattern of short signals, dots (·), and long signals, dashes (–). You can send it by flashing light, by sound, by radio, or by hand flags and arms. The International Code of Signals sets the symbols and the timing for ships.
Letters
A ·–; B –···; C –·–·; D –··; E ·; F ··–·; G ––·; H ····; I ··; J ·–––; K –·–; L ·–··; M ––; N –·; O –––; P ·––·; Q ––·–; R ·–·; S ···; T –; U ··–; V ···–; W ·––; X –··–; Y –·––; Z ––··
Figures
Figures have five elements. 1 to 5 start with dots: 1 ·––––, 2 ··–––, 3 ···––, 4 ····–, 5 ·····. 6 to 0 start with dashes: 6 –····, 7 ––···, 8 –––··, 9 ––––·, 0 –––––. For 1–5, count the leading dots. For 6–9, add 5 to the leading dash count. Five dashes means 0.
Timing
The dot is the unit. A dash lasts 3 units. The gap between elements of one symbol is 1 unit, between letters 3 units, and between words or groups 7 units. The Code advises making dots slightly short, to keep them clearly different from dashes. Its standard rate for flashing light is 40 letters a minute; send slower and clearly rather than fast and wrong.
SOS
SOS, ···–––···, is a distress signal under COLREG Annex IV when made by any signalling method. Keep one-unit gaps between elements, but no letter gaps. Pause before repeating. Practise in pairs indoors, with the light hidden from outside view. Send five mixed letters or figures, write down what you receive, compare results, then repeat errors slowly. Swap roles and increase speed only when you both read accurately.
2Key data
- Dot
- 1 unit
- Dash
- 3 units
- Gaps
- Within a symbol 1; between letters 3; between words 7
- ICS standard rate (light)
- 40 letters per minute
- SOS
- ···–––··· with element gaps, no letter gaps
- Figures
- Five elements: 1 ·––––, 5 ·····, 6 –····, 0 –––––
3Key points
- 1
Dot 1 unit, dash 3; gaps of 1 within a symbol, 3 between letters, 7 between words.
- 2
Numerals use five elements. For 1–5, count leading dots; for 6–9, add 5 to leading dashes. Zero is five dashes.
- 3
Make dots slightly short so dots and dashes stay distinct.
- 4
Send SOS as one symbol: ···–––···. Keep element gaps; omit letter gaps.
4Frequent mistakes
Wrong: Decode a live signal by counting marks on a printed chart.
Right: Use the chart to check patterns during practice. Learn each letter’s rhythm so you can recognise it directly.
Wrong: Send SOS as three separate letters, S O S.
Right: Keep one-unit gaps between elements, but no letter gaps. Pause before repeating SOS.
Wrong: Speed proves skill, so send as fast as you can.
Right: Even rhythm and clear gaps matter more. A message sent slowly and read correctly is the only one that counts.
5Practice case & exam keys
Practising with a torch, your cadet sends ‘K’ as dash, short pause, dot, short pause, dash, but the pauses are as long as the dashes. You read ‘T E T’. What went wrong?
Show the answer
The gaps inside a symbol must be 1 unit, as long as a dot. Her gaps were 3 units, which is the gap between letters, so you read three letters instead of one. Ask her to keep the elements of K tight, –·–, and to leave 3 units only after the whole letter.
Exam keys
- Dot = 1 unit; dash = 3; gap in a symbol = 1; between letters = 3; between words = 7.
- Figures: five elements each; 0 is five dashes, 5 is five dots.
- SOS ···–––··· is a COLREG Annex IV distress signal by any method.
- ICS standard flashing-light rate: 40 letters per minute.
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