International Code of Signals

You may use the following calculator to decode a message, encoded by the International Code of Signals (ICS). ICS is used to transmit signals by use of visual, sound and radio communications.
The purpose of the International Code of Signals is to provide ways and means of communication in situations related essentially to safety of navigation and persons, especially when language difficulties arise.¹
The calculator converts the code into plain text, flag signal sequence and Morse code. A description of the flag signals follows the calculator.
The calculator supports one- and two-letter International signals. It interprets and substitutes signal parameters into the message, if any, in the code. A loose interpretation of Captain Grant's message from Jules Verne's famous novel is used as an example.

International Code of Signals Decoder

Code

ContextGeneral Icebreaker Vessel in icebreaker convoy In harbor Sound signal

Reference date

Reference date

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Century

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Message

 

Morse

 

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The code

The International Signal Code consists of

• Single-letter signals (very urgent, important, or of very common use)
• Two-letter signals for General Signal Code
• Three-letter signals beginning with “M” for Medical Signal Code (not supported by the calculator)

Some signals have different meanings in certain circumstances.
For example, when conducting icebreaker escort, special single-letter signals are used to communicate with the convoy. Use the Context selection list in the calculator to select the correct set of signals for the given situation.

In some cases, numerical complements are used if necessary to expand the meaning of the signal, to ask questions on the topic, to obtain standard answers, or to provide additional information.
Some messages require additional numerical data. These are encoded in the following format:

You may use the following calculator to correctly encode ICS message with all parameters:

International Code of Signals Encoder

SectionAll Procedural Distress—Emergency ...Abandon ...Accident ......Doctor ......Injured/Sick ...Aircraft—Helicopter ......Alight-Landing ......Communications ......Ditched—Disabled—Afloat ......Flying ......Parachute ......Search—Assistance ......Speed ......Helicopter ...Assistance ......Required ......Not required—Declined ......Given—Not Given ......Proceeding to Assistance ...Boats—Rafts ......Available ......Required ......Send ......Search ...Disabled—Drifting—Sinking ......Disabled ......Drifting ......Sinking ...Distress ......Vessel/Aircraft in Distress ......Distress Signal ......Position of Distress ......Contact or Locate ...Position ......Position of Distress ...Search and Resque ......Proceeding to Assistance ......Position of Distress or Accident ......Information—Instructions ......Search ......Results of Search ......Resque ...Survivors Casualities—Damages ...Collisions ...Damages—Repairs ...Diver—Underwater operations ...Fire-Explosion ......Fire ......Explosion ...Grounding—Beaching—Refloating ......Grounding ......Beaching ......Refloating ...Leak ...Towing—Tugs ......Tug ......Towing—Taking in Tow ......Towing Line—Cable—Hawser ......Make Fast—Veer ......Cast Off ......Engine Maneuvers Aids to navigation—Navigation—Hydrography ...Aids to navigation ......Buoys—Beacons ......Lights—Lightvessels ...Bar ...Bearings ...Canal—Channel—Fairway ......Canal ...Course ...Dangers to navigation—Warnings ......Derelict—Wreck—Shoal ......Radiation Danger ......Warning ...Depth—Draft ......Depth ......Draft ...Electronic navigation ......Radar ......Radio Direction Finder ...Mines—Minesweeping ...Navigation lights—Searchlight ...Navigating and steering instructions ...Tide Maneuvers ...Ahead—Astern ......Ahead—Headway ......Astern—Sternway ...Alongside ...To anchor—Anchor(s)—Anchorage ......To Anchor ......Anchor(s) ......Anchorage ...Engines—Propeller ......Engines ......Propeller ...Landing—Boarding ......Landing ......Boarding ...Maneuvers ...Proceed—Underway ......Proceed ......Underway ...Speed ...Stop—Heave to Miscellaneous ...Cargo—Ballast ...Maneuvers ...Fishery ...Pilot ...Port—Harbor ...Miscellaneous ......Exercises ......Bunkers ......Fumigation Meteorology—Weather ...Clouds ...Gale—Storm—Tropical storm ......Gale ......Storm ......Tropical storm ...Ice—Iceberg ......Ice ......Iceberg ...Icebreaker ...Atmospheric pressure—Temperature ......Atmospheric pressure ......Temperature ...Sea—Swell ......Sea ......Swell ...Visibility—Fog ...Weather—Weather Forecast ...Wind Routing of Ships Communications ...Acknowledge—Answer ...Calling ...Cancel ...Communicate ...Excercise ...Reception—Transmission ...Repeat International health regulations ...Pratique messages US/Russia supplementary signals for naval vessels

Search result

Number

Number

Position is set by

Azimuth and distance

Coordinates

Date

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Course

Azimuth

Vessel

Latitude 1

°

′

″

N

S

Longitude 1

°

′

″

E

W

Latitude 2

°

′

″

N

S

Longitude 2

°

′

″

E

W

Speed

knots

• knots
• km/h

AgroundOn rocky bottom. On soft bottom. Forward. Amidship. Aft. At high water forward. At high water amidship. At high water aft. Full length of vessel. Full length of vessel at high water.

AssistanceWater Provisions Fuel Pumping equipment Firefighting appliances Medical assistance Towing Survival craft Vessel to stand by Icebreaker

Ice developmentNo change. Ice situation has improved. Ice situation has deteriorated. Ice has been broken up. Ice has opened or drifted away. New ice has been formed and/or the thickness of the ice has increased. Ice has been frozen together. Ice has drifted into the area or has been squeezed together. Warning of pressure ridges. Warning of hummocking or ice screwing.

Effects of the ice on navigationUnobstructed. Unobstructed for power-driven vessels built of iron or steel, dangerous for wooden vessels without ice protection. Difficult for low-powered vessels without the assistance of an icebreaker, dangerous for vessels of weak construction. Possible without icebreaker only for high-powered vessels of strong construction. Icebreaker assistance available in case of need. Proceed in channel without the assistance of icebreaker. Possible only with the assistance of an icebreaker. Icebreaker can give assistance only to ships strengthened for navigation in ice. Temporarily closed for navigation. Navigation has ceased.

Character of iceNo ice. New ice (ice crystals, slush or sludge, pancake ice or ice rind). Young fast ice (5-15 cms thick or rotten fast ice). Open drift ice (not more than 5/8 of the water surface is covered by ice floes). A compressed accumulation of sludge (a compressed mass of sludge or pancake ice, the ice cannot spread). Winter fast ice (more than 15 cms in thickness). Close drift ice (the area is covered by ice floes to a greater extent than 5/8). Very close drift ice on open sea. Pressure ice or big, vast, heavy ice floes. Shore lead along the coast.

JettisoningCargo. Bunkers. Everything movable forward. Everything movable aft.

LanguageDutch English French German Greek Italian Japanese Norwegian Russian Spanish

Conditions of innocent passageBy threatening or using force against our/your sovereignty, territorial integrity, or political independence. By exercising or practicing with weapons. By engaging in acts aimed at collecting information to the prejudice of our/your defense or security. By engaging in acts of propaganda aimed at affecting our/your defense or security. By engaging in the launching, landing or taking on board of aircraft or a military device. By engaging in the loading or unloading of a commodity, currency or person contrary to the customs, fiscal, immigration or sanitary laws or regulations of our/your country. By engaging in willful and serious pollution. By engaging in fishing activities. By engaging in research or survey activities. By engaging in acts aimed at interfering with our/your systems of communication or other facilities or installations.

RhumbDirection unknown (or calm) Northeast East Southeast South Southwest West Northwest North All directions (or confused or variable)

Signaling methodMorse signaling by hand flags or arms Loud hailer (megaphone) Morse signaling lamp Sound signals

State of swellNo swell short or middle, weak—approximate height <2 m (6 ft.) Long, weak—approximate height <2 m (6 ft.) Short, moderate—approximate height 2-4 m (6-12 ft.) Middle, moderate—approximate height 2-4 m (6-12 ft.) Long, moderate—approximate height 2-4 m (6-12 ft.) Short, high—approximate height > 4 m (12 ft.) Middle, high—approximate height > 4 m (12 ft.) Long, high—approximate height > 4 m (12 ft.) Confused

State of seaCalm (glassy) 0m 0 ft Calm (rippled) 0-0.1m 0- 1 / 3 ft Smooth (wavelets) 0.1-0.5m 1/3 -1 2/3 ft Slight 0.5-1.2 m 1 2 / 3 -4 ft Moderate 1.25-2.5m 4-8 ft Rough 2.5-4m 8-13 ft Very rough 4-6m 13-20 ft High 6-9m 20-30 ft; Very high 9-14m 30-45 ft Phenomenal over 14m over 45 ft

Place

Distance in n.m.

Depth

ft

• ft
• m

Port

Object

Station

Vessel 2

Time

~

:

~

AM PM

local

• local
• UTC

Azimuth 2

Name

Station 2

Calculate

Code

 

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Flag signaling in ICS

The ICS system uses 26 flags corresponding to the letters of the English alphabet, 10 numerical pennants, 3 substitution pennants and an answering pennant.

	A - alpha		B - bravo		C - charlie		D - delta		E - echo
	F - foxtrot		G - golf		H - hotel		I - india		J - juliett
	K - kilo		L - lima		M - mike		N - november		O - oscar
	P - papa		Q - quebek		R - romeo		S - sierra		T - tango
	U - uniform		V - viktor		W - whiskey		X - X-ray		Y - yankee
	Z - zulu

Numerical pennants

	1 - unaone		2 - bissotwo		3 - terrathree		4 - cartefour		5 - pantafive
	6 - soxisix		7 - setteseven		8 - octoeight		9 - novenine		0 - nadazero

Substitute pennants

	1st - substitute		2nd substitute		3d substitute

Answering pennant

is used as a finishing flag, an acknowledgement of receipt flag and a decimal point.