CHAPTER I | EXPLANATIONS
1. 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. In the preparation of the Code, account was taken of the fact that wide application of radiotelephony and radiotelegraphy can provide simple and effective means of communication in plain language whenever language difficulties do not exist
2. The signals used consist of:
1. Single-letter signals allocated to significations which are very urgent, important, or of very common use.
2. Two-letter signals for the General Section.
3. Three -letter signals beginning with “M” for the Medical Section.
3. The Code follows the basic principle that each signal should have a complete meaning. This principle is followed throughout the Code; in certain cases complements are used, where necessary, to supplement the available groups.
4. Complements express:
1. Variations in the meaning of the basic signal.
“CP” = “I am (or vessel indicated is) proceeding to your assistance.”
“CP 1” = “SAR aircraft is coming to your assistance.”
2. Questions concerning the same basic subject or basic signal.
“DY” = Vessel (name or identity signal) has sunk in lat . . . long . . .”
“DY 4” = “What is the depth of water where vessel has sunk”
3. Answers to a question or request made by the basic signal.
“HX” = “Have you received any damage in collision”
“HX 1” = “I have received serious damage above the waterline.”
4. Supplementary specific or detailed information.
“IN” = “I require a diver.”
“IN 1” = “I require a diver to clear propeller.”
5. Complements appearing in the text more than once have been grouped in three tables. These tables should be used only as and when specified in the text of the signals.
6. Text in brackets indicates:
1. An alternative, e.g.: “(Or survival craft) …”;
2. Information which may be transmitted if it is required or if it is available, e.g.:”… (Position to be indicated if Necessary)”;
3. An explanation of the text.
7. The material is classified according to subject and meaning. Extensive cross referencing of the signals in the right-hand Column is used to facilitate coding.
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