Module 18 - Signals & Communications
International Code of Signals
What you will learn
Interpret Alpha, Bravo, Quebec and N over C accurately, then distinguish the signal's meaning from the skipper's separate navigation and local-compliance decisions.
Single-letter signals compress a standard meaning, but they do not remove context. Identify the hoist, confirm the maintained reference and act conservatively around the vessel or harbour concerned.
The International Code of Signals provides a standard set of flags, pennants, and meanings. Yachtmasters do not need to memorise the whole code, but they should recognise common safety flags and know where to find the full code in almanacs and publications.
Useful examples include A (Alpha), meaning ‘I have a diver down; keep well clear at slow speed’; B (Bravo), meaning ‘I am taking in, discharging, or carrying dangerous goods’; Q (Quebec), meaning ‘My vessel is healthy and I request free pratique’; and N over C, meaning distress. Local harbour instructions may also use signal flags or boards for traffic control.
| Signal | Code meaning | Operational caution |
|---|---|---|
| A / Alpha | Diver down; keep well clear at slow speed | Confirm the vessel and work area |
| B / Bravo | Taking in, discharging or carrying dangerous goods | Follow berth and harbour restrictions |
| Q / Quebec | Healthy vessel requests free pratique | Request is not the same as clearance |
| N over C | Distress and need of assistance | Use other available alerting and message detail too |
Read a flag before entering a work area
A vessel near the approach displays Alpha while a tanker at a berth displays Bravo and the harbour publishes local traffic lights.
1. Identify
Confirm the flag shape, colour, hoist and vessel rather than matching one colour from memory.
2. Translate
Alpha reports a diver down; Bravo reports taking in, discharging or carrying dangerous goods.
3. Apply context
Keep well clear at slow speed around the diver and obey the separate harbour instructions, traffic and depth limits.
Sense check: The crew can state the code meaning and the independent local or collision-avoidance decision it informs.
Common mistake or limitation
- Bravo is more precise than the shorthand ‘dangerous goods’: it covers taking in, discharging or carrying them.
- Quebec requests free pratique; displaying it does not itself prove that clearance has been granted.
- N over C is a distress signal, not a substitute for giving position and assistance information by an available communication path.
- Local signal systems may use flags or boards differently; check current harbour instructions rather than guessing from colour alone.
Recap
- Alpha — diver down; keep well clear at slow speed.
- Bravo — taking in, discharging or carrying dangerous goods.
- Quebec — vessel healthy and requesting free pratique.
- N over C — distress and need of assistance.
Optional quick check
Section 7 of 18
A vessel displays Quebec on arrival. What does the signal establish?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying Signals & Communications
This public lesson is part of Revision Module 18. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.