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Commentary - Other means of communication
    [p.1269] Annex I, Article 11 -- Other means of communication

    4253 The draft text on other means of communication submitted by the ICRC -- Article 12 of draft Annex I -- referred to Annex 12 to the Chicago Convention on International Civil Aviation of 7 December 1944. This Annex is entitled "Search and rescue" and it is applicable to the search and rescue services in the territories of Contracting States and on the high seas, and to the co-ordination of such services between States. Chapter 5.10 and Appendix A of Annex 12 provide for aircraft and ships to exchange visual signals for search and rescue purposes and [p.1270] also refers to two ground-to-air visual signal codes for use by survivors and search parties.

    4254 Other visual and light signals for search. and rescue are given in the ICAO Search and Rescue Manual, Part 2, Chapter 2, "Communications". They include paulin signals and body signals in the ground-to-air visual signal codes for use by ground search parties and survivors. (1)

    4255 It may be assumed that crews of medical aircraft are familiar with these visual means of communication, which are described in international search and rescue procedures. However, it would be advisable for the personnel of other medical units and transports to receive some training in this area as well, so that, if necessary, visual signals may be used in time of armed conflict, subject to the approval of the competent authority.

    4256 In order to avoid any differences of interpretation when these visual signals are used in medical evacuation or search and rescue operations, the Parties to the conflict could notify one another of their intention to use such signals, under the agreements concluded in respect of such operations.

    4257 The methods to be used for sending the visual signals concerned are described in the Search and Rescue Manual, Part 2, Chapter 2, Section 2.3.3:

    "2.3.3. ' Ground-Air Visual Signal Code for Use by Land parties ' When a land party wishes to inform an aircraft of the progress of the search and/or rescue, it should use the appropriate symbols described in Figures 2-1 and 2-2. The symbols shown in Figures 2-1 and 2-2A may be made of any available material, e.g., strips of fabric or parachute material, pieces of wood, stones, snow blocks, etc., or by digging shadow-throwing trenches. The symbols should be at least 8 ft (2.5 m) long and provide as much colour contrast as possible with the background. The symbols shown in Figure 2-2B are the so-called paulin or panel signals and are made by folding a paulin, a type of rubber poncho, provided in a life-raft. They are neon-red on one side and non-specular blue on the other (other models are yellow-orange and sea-blue)."

    4258 Chapter 4 and Appendix A of ICAO Annex 2, "Rules of the Air", refer to other visual signals used for giving aircraft clearance to approach, land and taxi on aerodromes.

    4259 Section 3 of Appendix A describes the visual signals used to warn an unauthorized aircraft flying in, or about to enter a restricted, prohibited or danger area. They consist of a series of projectiles discharged from the ground at intervals of ten seconds, each showing, on bursting, red and green lights or stars. They indicate that the aircraft is to take such action as may be necessary to leave the area. These are not the interception signals referred to in Article 13 ' (Signals and procedures for the interception of medical aircraft) ' below.

    [p.1271] 4260 The IMO International Code of Signals contains detailed instructions on visual transmission methods:

    -- ' Flag signalling: ' the International Code's set of signal flagsconsists of 26 alphabetical flags, 10 numeral pendants, 3 substitutes and the answering pendant. Messages are always coded using the Code's letter groups.
    -- ' Flashing light and sound signalling: ' international Morsesymbols are used; they represent letters and numerals and are expressed by dots (short) and dashes (long). Theoretically, a dash is equivalent to three dots. Luminous Morse signals are sent by showing and covering a light. Sound Morse signals consist of long and short blasts produced by a siren, a whistle, a foghorn or any other sound-producing device.
    -- ' Morse signalling by arms: ' this method is described in Chapter IX of the Code by means of a table showing how the arms are lifted or stretched to form a dot or a dash. A flag may be held in each hand. Signals may be sent without a flag or using one arm only; this Morse signalling method has replaced the former system of semaphore signalling by arms. If a time count is kept, the message will necessarily conform to the Code's groups. The use of international codes calls for familiarity with the compulsory procedure to be used for each method of transmission. Practice is also necessary in order to achieve a satisfactory visual signalling rate. For example, the standard rate of Morse signalling by flashing light is eight words per minute.

    4261 Visual signalling using international codes is the last means of communication left in situations where there are no wire or radio links and a messenger cannot be sent.

    ' Ph. E. '

    NOTES (1) [(1) p.1270] ICAO, Doc. 7333-AN/859, ' Search and Rescue Manual ', Parts 1 and 2, ICAO, Montreal, 3rd edition, 1970;