Whistle means any sound-signaling appliance that
is capable of producing the prescribed blast and that
complies with the specifications in Annex III of the
International and Inland Rules. (When your ship was
built and the whistle was installed, all the specifications
listed in Annex III were considered.)
Short blast means a blast about l-second long.
Prolonged blast means a blast from 4-seconds to
Meeting (or head-on) situation defines a situation
in which, by day, the masts of each vessel, when viewed
from the other, are in a line.
Crossing situation defines the situation where each
vessel has the other any place forward of 22.5° abaft of
Overtaking situation describes the situation where
one vessel approaches the other from anyplace more
than 22.5° abaft of either beam.
MANEUVERING AND WARNING SIGNALS
Since there are major differences between the
International and the Inland maneuvering and warning
signals, they will be presented separately, and the
differences will be noted on the inland version.
When vessels are in sight of one another, a
power-driven vessel underway, when maneuvering as
authorized or required by these rules, must indicate that
maneuver by the following signals on the whistle:
One short blast I AM ALTERING MY COURSE
Two short blasts I AM ALTERING MY COURSE
Three short blasts I AM OPERATING ASTERN
Any vessel may supplement the whistle signals
prescribed above by light signals, repeated as
appropriate while the maneuver is being carried out.
These light signals will have the following significance:
One flash I AM ALTERING MY COURSE TO
Two flashes I AM ALTERING MY COURSE TO
Three flashes-I AM OPERATING ASTERN
The duration of each flash will be is about 1 second;
the interval between flashes must be about 1 second; and
the interval between successive signals must be not less
than 10 seconds. The light used for this signal will be,
if fitted, an all-around white light visible at a minimum
range of 5 miles, and must comply with the provisions
of Annex I that pertain to the International Rules.
When in sight of another in a narrow channel or
fairway, and action is required by the vessel being
overtaken, the vessel intending to overtake another must
indicate its intention by the following signals on the
Two prolonged blasts followed by one short blast I
INTEND TO OVERTAKE YOU ON YOUR
Two prolonged blasts followed by two short blasts I
INTEND TO OVERTAKE YOU ON YOUR PORT
The vessel about to be overtaken will indicate
agreement by the following signal on the whistle:
One prolonged, one short, one prolonged, and one
short blast, in that order
When vessels in sight of one another are
approaching each other and 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 must
immediately indicate such doubt by giving at least five
short, rapid blasts on the whistle. Such signal may be
supplemented by a light signal of at least five short, rapid
A vessel nearing a bend or an area of a channel or
fairway where other vessels may be obscured by an
intervening obstruction must sound one prolonged blast.
Such signal must be answered with a prolonged blast by
any approaching vessel that may be within hearing
around the bend or behind the intervening obstruction.
If whistles are fitted farther apart than 100 meters
on a vessel, only one of the whistles will be used for
giving maneuvering and warning signals.
These last three paragraphs apply to Inland Rules as
well as International Rules.