Signalling & Communication
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TermDefinition
- Flag / Pennant, Signals & Communication Code Flag Sierra (S)

The International Maritime Signal Flag Sierra.
Meaning
I am operating astern propulsion.
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If appended with a Numeral Pennant, Speed... - Flag / Pennant, Signals & Communication Second Substitute (ICS Flag)

Substitute or repeater flags allow messages with duplicate characters to be signalled without requiring multiple sets of flags.
- General Nautical Terminology, Safety, Signals & Communication Sécurité
A maritime safety message broadcast over radio to convey important but non-urgent navigational or weather-related information.
Sécurité is a...
More Details - Flag Semaphore, Morse Code, Signals & Communication Semaphore
A signalling system used to convey information at a distance by means of visual signals, typically using flags or lights.
Semaphore is a...
More Details - Phonetic Alphabet, Signals & Communication Sierra
Pronounced: see-AIR-rah
The term for the letter S in the NATO Phonetic Alphabet.
- Flag Semaphore, Signals & Communication Letter S (Flag Semaphore)

Flag semaphore indicating the letter S.
- Morse Code, Signals & Communication Letter S (Morse Code)
International Morse Code sequence representing the letter S.
- General Nautical Terminology, Morse Code, Safety, Signals & Communication SOS
The universally recognised distress signal used in maritime communication to indicate an emergency requiring immediate assistance.
The German...
More Details - Flag Semaphore Space (Flag Semaphore)

This shape indicates a space, usually between words. The same shape is also used for Rest (Flag Semaphore) & Ready (Flag Semaphore).
More Details - General Nautical Terminology, Signals & Communication Standard Marine Communication Phrases (SMCP)
A set of internationally agreed-upon phrases used to ensure clear, concise, and unambiguous communication at sea, particularly between vessels...
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