Free international COLREGs micro-course
Five short lessons combine synthesised horn, bell, and gong audio with visual blast strips, flashcards, a generated quiz, and the Fog Watch listening game.
Independent learning based on the IMO COLREGs structure. Audio timing is illustrative, not a signalling appliance. National rules, inland rules, current notices, lookout, safe speed, and practical seamanship remain separate.
Free reference chart
Play any pattern or read the identical visual timing strip. Real Rule 35 repetition intervals stay visible even though practice playback compresses the wait.
Rule 34(a) · manoeuvring
one short blast. Practice playback compresses only the wait before repetition.
A power-driven vessel in sight is altering course to starboard.
One short: my course is changing to starboard.
Rule 34(a) · manoeuvring
2 short blasts. Practice playback compresses only the wait before repetition.
A power-driven vessel in sight is altering course to port.
Two short: my course is changing to port.
Rule 34(a) · manoeuvring
3 short blasts. Practice playback compresses only the wait before repetition.
A power-driven vessel in sight is operating astern propulsion.
Three short means the engines are working astern; it does not prove movement astern.
Rule 34(d) · manoeuvring
5 short blasts. Practice playback compresses only the wait before repetition.
At least five short rapid blasts express doubt about another vessel's intentions or action.
I do not understand, or I doubt your action is enough.
Rule 34(c)(i) · manoeuvring
2 prolonged blasts, then one short blast. Practice playback compresses only the wait before repetition.
In a narrow channel, a vessel proposes overtaking on the other vessel's starboard side.
Two long and one short proposes passing on your starboard side.
Rule 34(c)(i) · manoeuvring
2 prolonged blasts, then 2 short blasts. Practice playback compresses only the wait before repetition.
In a narrow channel, a vessel proposes overtaking on the other vessel's port side.
Two long and two short proposes passing on your port side.
Rule 34(c)(ii) · manoeuvring
one prolonged blast, then one short blast, then one prolonged blast, then one short blast. Practice playback compresses only the wait before repetition.
The vessel to be overtaken agrees to the proposed narrow-channel overtaking manoeuvre.
Long-short-long-short is agreement, not a command to overtake.
Rule 34(e) · manoeuvring
one prolonged blast. Practice playback compresses only the wait before repetition.
A vessel nearing a blind bend or obscured channel area warns traffic that may be hidden.
One long blast around the blind corner; an approaching vessel answers.
Rule 35(a) · restricted visibility
one prolonged blast. Practice playback compresses only the wait before repetition.
A power-driven vessel making way through the water in restricted visibility.
One long at no more than two-minute intervals: powered and making way.
Rule 35(b) · restricted visibility
2 prolonged blasts. Practice playback compresses only the wait before repetition.
A power-driven vessel underway but stopped and making no way through the water.
Two long with about two seconds between them: underway, but stopped in the water.
Rule 35(c) · restricted visibility
one prolonged blast, then 2 short blasts. Practice playback compresses only the wait before repetition.
The shared restricted-visibility signal for sailing, fishing, NUC, RAM, constrained-draught and towing vessels.
One long and two short identifies a vessel whose type or work changes her manoeuvring picture.
Rule 35(e) · restricted visibility
one prolonged blast, then 3 short blasts. Practice playback compresses only the wait before repetition.
If manned, the last vessel of a tow sounds this after the towing vessel's signal when practicable.
The tow answers one long and three short behind the towing vessel.
Rule 35(g) · anchored aground
one rapid bell for about five seconds. Practice playback compresses only the wait before repetition.
A vessel at anchor under 100 metres rings the bell rapidly for about five seconds forward.
Rapid bell every minute: a vessel is anchored.
Rule 35(g) · anchored aground
one rapid bell for about five seconds, then one rapid gong for about five seconds. Practice playback compresses only the wait before repetition.
An anchored vessel of 100 metres or more rings a bell forward, followed by a gong aft.
Bell then gong shows a large vessel at anchor and helps reveal her length.
Rule 35(g) · anchored aground
one short blast, then one prolonged blast, then one short blast. Practice playback compresses only the wait before repetition.
An anchored vessel may add this warning to alert an approaching vessel to her position and collision risk.
Short-long-short is an optional anchored-vessel warning.
Rule 35(h) · anchored aground
3 distinct bell strokes, then one rapid bell for about five seconds, then 3 distinct bell strokes. Practice playback compresses only the wait before repetition.
An aground vessel adds three distinct bell strokes before and after the rapid anchor bell signal.
Three strokes, rapid bell, three strokes: aground. A vessel 100 metres or more also sounds the gong aft.
Rule 35(j) · pilot identity
4 short blasts. Practice playback compresses only the wait before repetition.
A pilot vessel on pilotage duty may add four short identity blasts to her applicable fog signal.
Four short is an optional pilot identity addition, not the full fog signal by itself.
Lesson 1 of 5
A short blast lasts about one second; a prolonged blast lasts four to six seconds. Rule 34 manoeuvring signals apply when vessels are in sight, while Rule 35 sound patterns describe vessels in or near restricted visibility. Keep context attached to rhythm.
Short, prolonged, bell, and gong
Use the visual strip and synthesised sound together. Timing is illustrative rather than a calibrated signalling appliance; the written duration and interval remain the learning reference.