PREFACE
Pub. 102, the 1969 edition of the International Code of Signals, became effective on 1 April 1969, and at that time
superseded H.O. Pubs. 103 and 104, International Code of Signals, Volumes I and II. All signals are contained in a single
volume suitable for all methods of communication.
The First International Code was drafted in 1855 by a Committee set up by the British Board of Trade. It contained 70,000
signals using eighteen flags and was published by the British Board of Trade in 1857 in two parts; the first containing
universal and international signals and the second British signals only. The book was adopted by most seafaring nations.
This early edition was revised by a Committee set up in 1887 by the British Board of Trade. The Committee’s proposals
were discussed by the principal maritime powers and at the International Conference in Washington in 1889. As a result,
many changes were made. The Code was completed in 1897 and was distributed to all maritime powers. That edition of the
International Code of Signals, however, did not stand the test of World War I.
The International Radiotelegraph Conference at Washington in 1927 considered proposals for a new revision of the Code
and decided that it should be prepared in seven languages, namely in English, French, Italian, German, Japanese, Spanish
and in one Scandinavian language which was chosen by the Scandinavian Governments to be the Norwegian language. The
new edition was completed in 1930 and was adopted by the International Radiotelegraph Conference held in Madrid in
1932. The new Code was compiled in two volumes, one for use by visual signaling and the other by radiotelegraphy. Words
and phrases applicable to aircraft were introduced in Volume II together with a complete Medical Section and a Code for
accelerating the granting of pratique. The Medical Section and the pratique signals were prepared with the assistance and
by the advice of the Office International d’Hygiene Publique. The Code, particularly Volume II, was primarily intended for
use by ships and aircraft and, via coastal radio stations, between ships or aircraft and authorities ashore. A certain number
of signals were inserted for communications with shipowners, agents, repair yards, etc. The same Conference (Madrid,
1932) established a Standing Committee to review the Code, if and when necessary, to give guidance on questions of use
and procedure, and to consider proposals for modifications. Secretarial duties were undertaken by the Government of the
United Kingdom. The Standing Committee met only once in 1933 and introduced certain additions and amendments.
The Administrative Radio Conference of the International Telecommunication Union suggested in 1947 that the
International Code of Signals should fall within the competence of the Inter-Governmental Maritime Consultative
Organization (IMCO). In January 1959, the First Assembly of IMCO decided that the Organization should assume all the
functions then being performed by the Standing Committee of the International Code of Signals. The Second Assembly in
1961 endorsed plans for a comprehensive review of the International Code of Signals intended to meet the present day
requirements of mariners. A Subcommittee of the Maritime Safety Committee of the Organization was established to revise
the Code, to prepare it in nine languages, namely the original seven (English, French, Italian, German, Japanese, Spanish,
and Norwegian) together with Russian and Greek, and to consider proposals for a new radiotelephone Code and its relation
to the International Code of Signals. The Subcommittee consisted of representatives of the following countries: Argentina,
Germany, France, Greece, Italy, Japan, Norway, Russian Federation, United Kingdom, and the United States of America.
The following international governmental and nongovernmental organizations contributed to, and assisted in, the
preparation of the revised Code: the International Atomic Energy Agency, the International Civil Aviation Organization,
the International Labor Organization, the International Telecommunication Union, the World Meteorological Organization,
the World Health Organization, the International Chamber of Shipping, the International Confederation of Free Trade
Unions, and the International Radio Maritime Committee.
The Subcommittee completed the revision of the Code in 1964, taking into account Recommendation 42 of the 1960
Conference on Safety of Life at Sea and Recommendation 22 of the Administrative Radio Conference, Geneva 1959. The
Code was adopted by the Fourth Assembly of IMCO in 1965. Since then, amendments to the Code have been adopted by
the Maritime Safety Committee and this publication incorporates all such amendments up to the 73
rd
session of the
Committee in December 2000 and adopted in July 2002.
The revised Code is intended to cater primarily for situations related essentially to safety of navigation and persons,
especially when language difficulties arise. It is suitable for transmission by all means of communication, including
radiotelephony and radiotelegraphy, thus obviating the necessity for a separate radiotelephone Code and dispensing with
Volume II for Radiotelegraphy. The revised Code embodies the principle that each signal has a complete meaning. It thus
leaves out the vocabulary method which was part of the old Code. The Geographical Section, not being considered essential,
was omitted. By these means it was possible to reduce considerably the volume of the Code and achieve simplicity.
The U.S./Russia Supplementary Signals for Naval Vessels Appendix was been reviewed and updated in 2020 by the Of-
fice of Chief of Naval Operations, Navy Plans, Policy, and Integration for Russia, Ukraine, and Arctic.
Important information to amend material in this publication is updated as needed and made available as a fully corrected
publication, which can be downloaded from the NGA Maritime Domain web site: https://msi.nga.mil/Publications/ICOS.
Users should refer information and comments to: MARITIME SAFETY OFFICE, MAIL STOP N64-SFH, NATIONAL
GEOSPATIAL-INTELLIGENCE AGENCY, 7500 GEOINT DRIVE, SPRINGFIELD, VIRGINIA, 22150-7500. E-mail: