Sound and light signals
Segnali sonori e luminosi · 9 parti · 7 figure · 35 min
Short and prolonged blasts, manoeuvring signals between vessels in sight, doubt and overtaking signals, and fog signals for every type of vessel (power-driven, sailing, at anchor, aground, towed).
Two situations, two sound languages
Due situazioni, due linguaggi di suoni
There are two groups of sound signals: those used when vessels are in sight of one another (Rule 34) and those used in restricted visibility (Rule 35). When vessels are in sight of one another the sound says what I am about to do: altering course, going astern, wishing to overtake, or I do not understand. In restricted visibility (Rule 35) the sound says who I am and how I am moving, because nobody can see anyone and the signal only serves to be heard. Signals are made with two lengths only: the short blast and the prolonged blast.
'In sight of one another' means that one vessel can be observed visually from the other: radar is not enough. 'Restricted visibility' means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes. These are two different conditions, and each has its own series of sounds.
| Vessels in sight (Rule 34) | Restricted visibility (Rule 35) | |
|---|---|---|
What the sound says | What I am about to do: altering course, going astern, overtaking you, not understanding. | Who I am and how I am moving: it serves only to make yourself heard. |
When | We can see each other by eye. | In or near an area of restricted visibility, by day and by night. |
Who makes it | Mainly the power-driven vessel that is manoeuvring. | Every vessel, according to her type and how she is moving. |
In short
- The signals use only two lengths: the short blast and the prolonged blast.
- Do not mix up the two sets: the same sound has different meanings.
Remember. In sight: the sounds say what I am doing. In fog: they say who I am.
Exam terms (4)
- Short blast
- suono breve
- Prolonged blast
- suono prolungato
- In sight of one another
- in vista una dall'altra
- Restricted visibility
- visibilità ridotta
Short blast and prolonged blast
Suono breve e suono prolungato
All signals are made with two lengths only: a short blast lasts about one second, a prolonged blast from four to six seconds. In the figure the dot is the short blast and the bar the prolonged blast. You need suitable equipment: a whistle from 12 m, a bell as well from 20 m, a gong as well from 100 m (with a tone that cannot be confused with the bell). The 'whistle' means any sound signalling appliance capable of producing the prescribed blasts and complying with Annex III. The bell is also used for anchoring and grounding; the gong is sounded aft after the bell forward. Under 12 m there is no obligation to carry a whistle, bell and gong, but some other means of making an efficient sound signal is needed.
From the rules: Regola 32
«(a) The word whistle means any sound signalling appliance capable of producing the prescribed blasts and which complies with the specifications in Annex III to these Regulations. (b) The term short blast means a blast of about one second's duration. (c) The term prolonged blast means a blast of from four to six seconds' duration.»
From the rules: Regola 33(a)
«(a) A vessel of 12 metres or more in length shall be provided with a whistle, a vessel of 20 metres or more in length shall be provided with a bell in addition to a whistle, and a vessel of 100 metres or more in length shall, in addition, be provided with a gong, the tone and sound of which cannot be confused with that of the bell. The whistle, bell and gong shall comply with the specification in Annex III to these Regulations. The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the required signals shall always be possible.»
From the rules: Regola 33(b)
«(b) A vessel of less than 12 metres in length shall not be obliged to carry the sound signalling appliances prescribed in paragraph (a) of this Rule but if she does not, she shall be provided with some other means of making an efficient sound signal.»
In short
- Short blast: about 1 second.
- Prolonged blast: 4 to 6 seconds.
- A whistle is compulsory from 12 m; a bell as well from 20 m; a gong as well from 100 m.
- Under 12 m there is no obligation, but you need some other means of making an efficient sound signal.
Remember. Short ≈ 1 second. Prolonged 4-6 seconds.
Exam terms (3)
- Whistle
- fischio
- Bell
- campana
- Gong
- gong
Manoeuvring signals: 1, 2, 3 short blasts
Segnali di manovra: 1, 2, 3 brevi
With vessels in sight of one another, a power-driven vessel underway that is manoeuvring must say so to the others, and the number of short blasts grows with the manoeuvre: one, I am altering my course to starboard; two, I am altering my course to port; three, I am operating astern propulsion. These signals say what I am doing, and in fog the same sounds do not have this meaning. They can be repeated by light, if fitted an all-round white light visible at a minimum range of 5 miles: one flash, two flashes, three flashes. Each flash lasts about one second, the interval between flashes is about one second, and at least ten seconds pass between successive signals.
From the rules: Regola 34(a)
«(a) When vessels are in sight of one another, a power-driven vessel underway, when manoeuvring as authorized or required by these Rules, shall indicate that manoeuvre by the following signals on her whistle: one short blast to mean "I am altering my course to starboard"; two short blasts to mean "I am altering my course to port"; three short blasts to mean "I am operating astern propulsion".»
From the rules: Regola 34(b)(i)
«(b) Any vessel may supplement the whistle signals prescribed in paragraph (a) of this Rule by light signals, repeated as appropriate, whilst the manoeuvre is being carried out: (i) these light signals shall have the following significance: one flash to mean "I am altering my course to starboard"; two flashes to mean "I am altering my course to port"; three flashes to mean "I am operating astern propulsion";»
From the rules: Regola 34(b)(ii)(iii)
«(ii) the duration of each flash shall be about one second, the interval between flashes shall be about one second, and the interval between successive signals shall be not less than ten seconds; (iii) the light used for this signal shall, if fitted, be an all-round white light, visible at a minimum range of 5 miles, and shall comply with the provisions of Annex I to these Regulations.»
In short
- They apply to a power-driven vessel underway that is manoeuvring, with the vessels in sight.
- They may be supplemented by light: one flash, two flashes, three flashes.
- Each flash lasts about 1 second, as does the interval; between successive signals at least 10 seconds pass.
- The light, if fitted, is an all-round white light, visible at a minimum range of 5 miles.
Remember. One for starboard, two for port, three for astern: the number grows with the manoeuvre.
Watch out. These signals say "what I am doing": in fog the same sounds do not have this meaning.
Exam terms (2)
- Altering course to starboard
- accostare a dritta
- Astern propulsion
- macchine indietro
Overtaking in a narrow channel
Sorpasso in un canale stretto
In a narrow channel, with vessels in sight of one another, when the overtaking can take place only if the vessel to be overtaken has to take action to permit safe passing (Rule 9(e)(i)), a vessel that wants to overtake announces it with two prolonged blasts: the two long ones say 'overtaking', the short ones say on which side, one for starboard and two for port. The vessel about to be overtaken, if she agrees, answers with one prolonged, one short, one prolonged and one short blast; in the figure this is the last line. The doubt signal and the blind bend signal, which belong to the same rule, are explained in the next card.
From the rules: Regola 34(c)
«(c) When in sight of one another in a narrow channel or fairway: (i) a vessel intending to overtake another shall in compliance with Rule 9(e)(i) indicate her intention by the following signals on her whistle: two prolonged blasts followed by one short blast to mean "I intend to overtake you on your starboard side"; two prolonged blasts followed by two short blasts to mean "I intend to overtake you on your port side"; (ii) the vessel about to be overtaken when acting in accordance with Rule 9(e)(i) shall indicate her agreement by the following signal on her whistle: one prolonged, one short, one prolonged and one short blast, in that order.»
From the rules: Regola 34(d)
«(d) When vessels in sight of one another are approaching each other and from any cause either vessel fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least five short and rapid blasts on the whistle. Such signal may be supplemented by a light signal of at least five short and rapid flashes.»
From the rules: Regola 34(e)
«(e) A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction shall sound one prolonged blast. Such signal shall be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.»
In short
- In a narrow channel, with the vessels in sight, if the overtaking is possible only when the vessel to be overtaken has to take action, the overtaking vessel announces it.
- Two prolonged and one short: I intend to overtake on your starboard side.
- Two prolonged and two short: I intend to overtake on your port side.
- The vessel to be overtaken, if she agrees, replies: prolonged, short, prolonged, short.
Remember. Two long blasts say "overtaking". The short ones say which side: one starboard, two port.
Exam terms (2)
- Overtake
- sorpassare
- Narrow channel
- canale stretto
Doubt and blind bend
Dubbio e curva cieca
Two signals complete Rule 34. The first is doubt: if a vessel does not understand what the other is doing, or is in doubt whether she is taking enough action to avoid collision, she gives at least five short and rapid blasts, possibly with five rapid flashes. It applies to every vessel in sight, not only in a channel. The second is the blind bend: a vessel nearing a bend, or an obstruction that may hide other vessels, sounds one prolonged blast, and any vessel that hears it answers with one prolonged blast. If whistles are fitted more than 100 m apart, only one is used for these signals. The quotation is in the previous card.
In short
- Doubt: two vessels in sight, one does not understand what the other is doing or is not sure she is taking enough action to avoid collision.
- Signal: at least five short and rapid blasts, which may be supplemented by at least five rapid flashes.
- Blind bend: the vessel approaching sounds one prolonged blast; the vessel that hears it answers with a prolonged blast.
- If a vessel has several whistles more than 100 m apart, only one is used for these signals.
Remember. Five short = "I don't understand what you are doing, or I doubt that you are doing enough to avoid collision". One prolonged = "I am coming round the bend".
Watch out. The doubt signal applies to any vessels in sight, not only in a channel.
Exam terms (2)
- At least five short and rapid blasts
- almeno cinque suoni brevi e rapidi
- Bend
- curva cieca
At anchor and aground: bell and gong
All'ancora e incagliata: campana e gong
At anchor the sound is the bell: a vessel at anchor rings the bell rapidly for about 5 seconds at intervals of not more than one minute. If the vessel is 100 m or more in length, the bell forward and immediately afterwards the gong aft, again for about 5 seconds. In addition, to warn an approaching vessel, she may sound one short, one prolonged and one short blast. A vessel aground gives the same bell signal plus three separate and distinct strokes before and after the rapid ringing (in the figure: three strokes, rapid ringing, three strokes); she may add an appropriate whistle signal. A fishing vessel at anchor and a vessel restricted in her ability to manoeuvre working at anchor do not ring the bell: they sound one prolonged and two short blasts.
From the rules: Regola 35(d)(e)
«(d) A vessel engaged in fishing, when at anchor, and a vessel restricted in her ability to manoeuvre when carrying out her work at anchor, shall instead of the signals prescribed in paragraph (g) of this Rule sound the signal prescribed in paragraph (c) of this Rule. (e) A vessel towed or if more than one vessel is towed the last vessel of the tow, if manned shall at intervals of not more than 2 minutes sound four blasts in succession, namely one prolonged followed by three short blasts. When practicable, this signal shall be made immediately after the signal made by the towing vessel.»
From the rules: Regola 35(f)(g)
«(f) When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and shall give the signals prescribed in paragraphs (a) or (b) of this Rule. (g) A vessel at anchor shall at intervals of not more than one minute ring the bell rapidly for about 5 seconds. In a vessel of 100 metres or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about 5 seconds in the after part of the vessel. A vessel at anchor may in addition sound three blasts in succession, namely one short, one prolonged and one short blast, to give warning of her position and of the possibility of collision to an approaching vessel.»
From the rules: Regola 35(h)
«(h) A vessel aground shall give the bell signal and if required the gong signal prescribed in paragraph (g) of this Rule and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell. A vessel aground may in addition sound an appropriate whistle signal.»
From the rules: Regola 35(i)(j)
«(i) A vessel of 12 metres or more but less than 20 metres in length shall not be obliged to give the bell signals prescribed in paragraphs (g) and (h) of this Rule. However, if she does not, she shall make some other efficient sound signal at intervals of not more than 2 minutes. (j) A vessel of less than 12 metres in length shall not be obliged to give the above-mentioned signals but, if she does not, shall make some other efficient sound signal at intervals of not more than 2 minutes.»
In short
- At anchor: the bell rung rapidly for about 5 seconds, at intervals of not more than one minute.
- From 100 m upwards: the bell forward followed immediately by the gong aft for about 5 seconds.
- To warn an approaching vessel she may add one short, one prolonged and one short blast.
- Aground: as at anchor, plus three separate and distinct strokes on the bell before and after the rapid ringing.
Remember. Anchor: rapid bell for 5 seconds every minute. Aground: three strokes, bell, three strokes.
Watch out. A fishing vessel at anchor and a vessel restricted in her ability to manoeuvre working at anchor do not ring the bell: they sound one prolonged and two short blasts.
Exam terms (3)
- Bell
- campana
- Gong
- gong
- Aground
- incagliata
Common mix-ups about signals
Confusioni tipiche sui segnali
The commonest confusions come from mixing up the two series. The signals of Rules 34 and 35 are not interchangeable: three short blasts in sight mean 'astern propulsion', while in fog the sounds are different and tell the type of vessel. One prolonged and two short blasts does not simply mean 'I am a sailing vessel': it belongs to six categories of vessel. Under 12 m, in fog, you may not stay silent: an efficient sound signal is needed at intervals of not more than 2 minutes, even with a hand horn. And a short blast lasts about one second, not one to two, while a prolonged blast lasts four to six seconds. To attract attention another signal may be made (Rule 36), provided it cannot be mistaken for any prescribed signal; distress signals are in Annex IV (Rule 37) and are not covered here.
| Mix-up | What is really true |
|---|---|
Three short blasts always mean the same thing | In sight: engines going astern. In fog the sounds tell the type of vessel |
One prolonged and two short: "I am sailing" | It is the signal of six categories of vessel with a limitation |
Under 12 m, in fog, you can stay silent | No: an efficient signal is needed at intervals of not more than 2 minutes, even with a hand horn |
The short blast lasts 1-2 seconds | Short: about 1 second. Prolonged: 4 to 6 seconds |
In short
- To attract attention you may make another signal, provided it cannot be mistaken for any prescribed signal (Rule 36).
- Distress signals are in Annex IV (Rule 37).
Remember. First ask yourself: can we see each other or not? Then choose the set of sounds.
Exam terms (2)
- Short blast
- suono breve
- Prolonged blast
- suono prolungato
In short: what to remember
In sight: the sounds say what I am doing. In fog: they say who I am.
Short ≈ 1 second. Prolonged 4-6 seconds.
One for starboard, two for port, three for astern: the number grows with the manoeuvre.
Two long blasts say "overtaking". The short ones say which side: one starboard, two port.
Five short = "I don't understand what you are doing, or I doubt that you are doing enough to avoid collision". One prolonged = "I am coming round the bend".
One long: I am moving. Two long: I am stopped but underway.
Prolonged + two short: I have a limitation. Prolonged + three short: I am the vessel towed.
Anchor: rapid bell for 5 seconds every minute. Aground: three strokes, bell, three strokes.
First ask yourself: can we see each other or not? Then choose the set of sounds.
Fine del capitolo
Quiz di fine capitolo · 5 domandeFonti: COLREG (MSN 1781) Regole 32, 33, 34, 35, 36, 37; Flip Card Fog Signal (carte 1-19); Sound Signal.JPG