Seaman's Handbook
PART C. Lights and Shapes : Sound signals in restricted visibility
In or near an area of restricted visibility, whether by day or night, the signals prescribed in this
Rule shall be used as follows:(a) A power-driven vessel making way through the water shall sound at intervals of not more
than 2 minutes one prolonged blast.(b) A power-driven vessel underway but stopped and making no way through the water shall
sound at intervals of not more that 2 minutes two prolonged blasts in succession with an
interval of about 2 seconds between them.(c) A vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel
constrained by her draught, a sailing vessel, a vessel engaged in fishing and a vessel
engaged in towing or pushing another vessel shall, instead of the signals prescribed in
paragraphs (a) or (b) of this Rule, sound at intervals of not more that 2 minutes three blasts in
succession, namely one prolonged followed by two short blasts.(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 in more that 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 blast followed by three short blasts. When practicable, this signal shall be made
immediately after the signal made by the towing vessel.(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) or 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 of 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 short 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.(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.(i) 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 that 2 minutes.(j) A pilot vessel when engaged on pilotage duty may in addition to the signals prescribed in
paragraphs (a), (b) or (f) of this Rule sound an identity signal consisting of four short blasts.(k) A pilot vessel when engaged on pilotage duty may in addition to the signals prescribed in
paragraphs (a), (b) or (g) of this Rule sound an identity signal consisting of four short blasts.
