Posted by: SherlockHomesSY | February 5, 2012

Communications Signaling

International Code Flags

International Code Flags & Pennants

V. Communications

A. Radio Telephone (90-93)
B. Communications Signaling (93-96)

B. Communications Signaling


Q5c Safety: Draw the International Code flags and pennants from memory and give the single-letter meanings of the flags.  Show how to use the International Code of Signals.


Ensign: For the USA, upper hoist canton (blue field w/ stars)
Hoist: Signal cluster of flags
Dip: ¾ of the way up the halyard
Close Up: All the way up the halyard


International Flags and Pennants, Sea Scout Manual, Appendix

Allied Flag Hoist Procedures

Flag Signaling at Sea

0. Introduction
– Signaling is carried out several ways
— Radio
— Global Marine Distress Signaling System
— International Code flags
— Signal flags (Semaphore)
— Blinker lights
— Rescue 21

– The International Code of Signals (ICS) is an international system of signals and codes for use by vessels to communicate important messages regarding safety of navigation and related matters.
— Signals can be sent by flag hoist, signal lamp (“blinker”), flag semaphore, radiotelegraphy, and radiotelephony.
— The International Code is the most recent evolution of a wide variety of Maritime flag signaling systems.

1. International Morse Code
– Morse code is frequently used in non-telegraphy signaling
– It can be simulated by several means
— Lights
— Horns
— Whistles
— Sirens
— Signal flag
– The most important one is SOS
— 3 dits followed by 3 dahs followed by 3 dits . . . .

2. Semaphore
– It is the fastest way of sending messages by flags
– It can only be used during daylight hours at short distances

3. International Code Flags
– Use of International Code flags is in the International Code of Signals
— Published by US Naval Oceanographic Office (NAVO)

The International Code of Signals has been reduced to focus on navigation and safety, including a medical section. Signals can be sorted into three groups:

  • Single-letter signals which are very urgent, important, or common.
  • Two-letter signals for other messages, sometimes followed with a numeric “complement” that supplements or modifies the message.
  • Three-letter signals beginning with “M” – these are the Medical Signal Codes.

In some cases additional characters are added to indicate quantities, bearing, course, distance, date, time, latitude, or longitude. There is also provision for spelling words, and for indicating use of other codes.

– One-flag signals are urgent or very common signals.
– Two-flag signals are mostly distress and maneuvering signals.
– Three-flag signals are for points of the compass, relative bearings, standard times, verbs, punctuation, also general code and decode signals.
– Four-flags are used for geographical signals, names of ships, bearings, etc.
– Five-flag signals are those relating to time and position.
– Six-flag signals are used when necessary to indicate north or south or east or west in latitude and longitude signals.
– Seven-flags are for longitude signals containing more than one hundred degrees.

4. How to Make an International Code Flag Signal

Note: This section, as written the Sea Scout manual, is confusing because new terms or over loaded terms are used without definition or explanation.

The ensign, for code signaling, is the US flag’s upper left canton (blue field w/ stars)

For the purposes of code signaling, any halyard on the boat will do, except the one with the US flag on it.  Just be sure not to use a halyard required to maintain control of your boat.  The goal is to fly the “hoists” (signal clusters) where they can be best seen.  On a sailboat, that may be on the backstay, where the US flag may be flying.  If the backstay is used, remove the US flag first.  Then begin signaling.

Flag Hoist Positions– To make a signal, hoist your ensign with the code flag underneath it

– To begin signaling, identify who is being signaled.
— If it’s to everyone, no distinguishing signal is needed
— If it’s to a particular vessel, fly their distinguishing signal
— Distinguishing signals are pre-assigned and distributed
— If you don’t know the distinguishing signal, know ships answer with their distinguishing signal or answering pennant.  Use that.
— When you have been answered, haul down your code flag

– Signals should always be hoisted where they can be best seen, not necessarily the masthead
— “Hoists” are kept flying until the other ship raises their answering pennant “close up”
— When answered, take it down, and hoist a new signal cluster
— Repeat, until the conversation is complete

– When finished signaling, haul down your ensign

5. How to Answer an International Code Flag Signal
– On seeing a signal made by another ship, hoist your answering pennant at the “dip”
— A flag is at the “dip” when raised ¾ of the way up its halyard
— After recognizing and understanding the “hoist” (signal cluster), raise it “close up”
— A flag is “close up” when it’s at the top of the halyard

– Hoist the answering pennant where it can be seen best

– When recognizing and understanding the other ship’s signal cluster, raise your answering pennant “close up” (at the top of the halyard)
— Keep it there until the other ship hauls her “hoist” (signal cluster) down
— Lower it to the “dip”
— If you don’t recognize or understand the “hoist”, attach code signal flags to your answering pennant indicating your confusion and raise it back up to the “dip”

– Code flags come in various sizes
— 3’ x 3’ code flags are handy for Sea Scouts
— The typical convention is a 1/2 inch run for every foot of boat length
— The flag ratio is 5:4

– Signal flags need to be properly attached (bent)
— Halyard clips (snap hooks)
— Sheet bend
— Signal halyard bend
— Inglefield clips


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