Sound, Radio and Morse

1. Overview

Source: INTERNATIONAL MARITIME ORGANIZATION. International Code of Signals. London: IMO, 2005. Este capítulo cobre os Chapters VII (Sound Signalling), VIII (Radiotelephony) e X (Morse Symbols, Phonetic Tables and Procedure Signals) — markdown do Yuri, linhas 716–1000.

Syllabus: Anexo 2-B (bibliografia): International Code of Signals · Anexo 2-A, item VI Comunicações: VI.3.4 Métodos de sinalização; VI.3.6 Radiotelefonia.

This chapter puts together three chapters of the International Code of Signals that the syllabus treats as one topic: how ships exchange meaning once flags are not the medium. Chapter VII covers sound signalling, Chapter VIII covers radiotelephony procedure, and Chapter X supplies the technical backbone that every other chapter depends on — the Morse symbols, the two phonetic spelling tables, and the procedure signals used across voice, flashing light and flags/radio.

The syllabus items covered here are VI.3.4 (methods of signalling) and VI.3.6 (radiotelephony). Chapter X is the chapter a candidate returns to constantly: its tables are not background reading, they are the material itself, and the phonetic tables in particular are tested letter by letter.

Chapter VII, para. 1: "Owing to the nature of the apparatus used (whistle, siren, fog-horn, etc.) sound signalling is necessarily slow. Moreover, the misuse of sound signalling is of a nature to create serious confusion at sea."

2. Chapter VII — Sound Signalling

2.1 Why sound signalling is limited

Sound signalling depends on slow apparatus — whistle, siren, fog-horn — so the Code treats it as a last resort rather than a default channel. Signals other than the single-letter signals should be used only in extreme emergency, and never in frequented navigational waters; in fog, sound signalling should be reduced to a minimum.

2.2 The asterisk restriction and ice-breaker signals

Chapter VII closes with a specific warning about the one-letter signals marked with an asterisk (*) elsewhere in the Code. When made by sound, those signals may only be transmitted in compliance with the International Regulations for Preventing Collisions at Sea (COLREG) — sound signalling does not give a ship license to use them outside that framework. The same paragraph also points to single-letter signals reserved exclusively for communication between an ice-breaker and the vessels it is assisting.

Chapter VII, para. 3: "Masters are reminded that the one-letter signals of the Code which are marked *, when made by sound, may only be made in compliance with the requirements of the International Regulations for Preventing Collisions at Sea. Reference is also made to the single-letter signals provided for exclusive use between an ice-breaker and assisted vessels."

3. Chapter VIII — Radiotelephony

3.1 Governing principles and spelling

Chapter VIII opens by tying the Code to a wider framework: whenever the International Code of Signals is used because of a language difficulty, the principles of the Radio Regulations of the International Telecommunication Union (ITU) then in force have to be observed, and letters and figures are to be spelt in accordance with the spelling tables (covered in section 5 below). When coast and ship stations are called, the identity signals (call signs) or names shall be used.

3.2 Method of calling and form of reply

The call and the reply mirror each other, and the Code fixes both structures precisely. Each element may be repeated, but never more than three times per call.

Difficult names of stations should also be spelt. After contact has been established, the call sign or name need not be sent more than once.

3.3 CQ, INTERCO and plain-language groups

Calling all stations in the vicinity uses a single group, CQ (CHARLIE QUEBEC), sent no more than three times at each call. In order to indicate that Code groups of the International Code of Signals are following, the word INTERCO is inserted. Words of plain language may also be in the text when the signal includes names, places and similar detail, and in that case the group YZ (YANKEE ZULU) is inserted if necessary.

3.4 Waiting, receipt, repetition and end-of-transmission signals

Four short signals carry the mechanics of the exchange once contact is made.

4. Chapter X — Morse Symbols

4.1 The Morse alphabet and numerals

Chapter X supplies the two tables every other method of Morse-based signalling assumes as known: the alphabet and the ten numerals, each letter and figure reduced to a fixed sequence of dots and dashes.

4.2 Why certain letters are omitted

Certain letters are left out of the Morse list, and Chapter X gives three reasons for the omission.

Note: Certain letters, such as "ē", "ā", "ō", etc., have been omitted from this list of Morse symbols because: .1 they are not to be used internationally; .2 they are contained in local codes; and .3 some of them can be substituted by a combination of two letters.

4.3 Morse symbols for procedure signals

Chapter X also gives the Morse symbols of three procedure signals. Each symbol is the sequence of its own letters run together — AR is A (· -) followed by R (· - ·), AS is A followed by S (· · ·), AAA is A three times — and what makes them one signal rather than three letters is the rule stated at the head of the procedure-signal section: "A bar over the letters composing a signal denotes that the letters are to be made as one symbol".

5. Chapter X — Phonetic Tables

5.1 Letter-spelling table (A–Z)

For pronunciation of letters by radiotelephony or by voice over a loud hailer, each letter has a fixed code word — the same code words used to spell out identities and difficult names in Chapter VIII. The table reproduces both the English and French pronunciation of every one of the twenty-six code words; bold syllables mark the stressed part.

Note: The bold syllables are emphasized.

5.2 Figure-spelling table

Figures, the decimal point and the full stop have their own code words, separate from the letter-spelling set. The Code adds one observation about them: the second component of each code word is the code word used in the Aeronautical Mobile Service.

Note: Each syllable should be equally emphasized. The second component of each code word is the code word used in the Aeronautical Mobile Service.

6. Chapter X — Procedure Signals

Chapter X closes with the fixed list of procedure signals, organized by the transmission method that carries them — voice, flashing light, or flags/radiotelephony/radiotelegraphy — plus one table of signals valid across every form. A bar over the letters composing a signal denotes that the letters are to be made as one symbol.

6.1 Signals for voice transmission (radiotelephony or loud hailer)

6.2 Signals for flashing-light transmission

6.3 Signals for flags, radiotelephony and radiotelegraphy transmissions

6.4 Signals for use where appropriate in all forms of transmission

Sixteen signals close the chapter, valid regardless of the channel used to send them — from procedural markers like K (invitation to transmit) and OK (acknowledging correct repetition), to the polarity pair NO and C, and the question marker RQ.

Notes: 1 The procedure signals C, N or NO and RQ cannot be used in conjunction with single-letter signals. 2 Signals on COMMUNICATIONS appear on pages 116–119. 3 When these signals are used by voice transmission the letters should be pronounced in accordance with the letter-spelling table, with the exception of NO which in voice transmission should be pronounced as "NO".