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Discussion in 'Free Thoughts' started by sculptor, Jul 19, 2022.

  1. sculptor Valued Senior Member

    Messages:
    8,320
    on it's own
    meaningless
    but
    as a universal distress signal
    it has meaning
    derived from morse code
    for its simplicity
    ... --- ... (sos)
    and we use it still even though
    very few could use morse code today.
    ............ I wonder how much is still used without the media of it's origins?
     
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  3. James R Just this guy, you know? Staff Member

    Messages:
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    Here are some common maritime distress signals in use today:

    1. Radio
    "Mayday, mayday, mayday"
    "Pan pan, pan pan, pan pan" (for urgent messages that aren't emergencies)
    SOS in Morse (if speech can't get through).

    2. Flares
    Orange smoke flare (daylight) or red hand-held flare (night).

    3. To attract attention of other vessels and aircraft: sheet with a large "V" on it.

    4. To signal distress when a person can be seen from a distance: slowly raise and lower arms outstretched on both sides.

    5. Sound signalling: SOS in Morse.

    6. Flags: International code flags "N" over "C".

    7. GPS signalling: EPIRB and PLB beacons.
     
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  5. James R Just this guy, you know? Staff Member

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    Interesting trivia:
    • "SOS" does not stand for "Save Our Souls" or "Save our ship". It was chosen simply because the pattern of the letters SOS is easy in Morse code.
    • In sending a Morse SOS signal, the signal lacks the usual pauses between each letter. That is, "dot dot dot dash dash dash dot dot dot" is sent without any pauses.
    • Prior to "SOS", the usual telegraph distress signal was "CQD". The letters "CQ" indicated a general call to "all stations" to listen, and "D" meant "distress".
     
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  7. James R Just this guy, you know? Staff Member

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    More comprehensive list of distress signals at sea:
    • a gun or other explosive signal fired at intervals of about a minute;
    • a continuous sounding with any fog-signalling apparatus;
    • rockets or shells, throwing red stars fired one at a time at short intervals;
    • a signal made by any signalling method consisting of the group … — … (SOS) in the Morse Code;
    • a signal sent by radiotelephony consisting of the spoken word “Mayday”;
    • the International Code Signal of distress indicated by N.C.;
    • a signal consisting of a square flag having above or below it a ball or something resembling a ball;
    • flames on the vessel (as from a burning tar barrel, oil barrel, etc.);
    • a rocket parachute flare or a hand flare showing a red light;
    • a smoke signal giving off orange-coloured smoke;
    • slowly and repeatedly raising and lowering arms outstretched to each side;
    • a distress alert by means of digital selective calling (DSC) transmitted on VHF channel 70, or MF/HF on the frequencies 2187.5 kHz, 8414.5 kHz, 4207.5kHz, 6312 kHz, 12577 kHz or 16804.5 kHz;
    • a ship-to-shore distress alert transmitted by the ship’s Inmarsat or other mobile satellite service provider ship earth station;
    • signals transmitted by emergency position-indicating radio beacons (EPIRB);
    • approved signals transmitted by radiocommunication systems.
     
  8. DaveC426913 Valued Senior Member

    Messages:
    17,107
    I have wondered about this since the first war movie I watched

    Do Morse code messages contain pauses between the letters?

    I always thought they did not, and wondered how they could be correcly interpreted without blurring letters together.

    I surmised that the encoding for each letter was surely chosen to minimize blurring letters - e.g. common combos like t and h would have a pattern that was unique and not replicated by other combos.

    I also surmised that experienced radio operators were good at deduction: "Well, he's either saying 'DHSHXYHSJFR' or he's saying 'BRING BACK COOKIES'..."
     
  9. James R Just this guy, you know? Staff Member

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    Yes.

    The timing in Morse code is based around the length of one "dot".
    A "dash" should last 3 times as long as a dot.
    There is a gap between each individual dot or dash that is equal to the length of one dot.
    There is a gap between each character sent that is equal to the length of one dash.
    There is a gap between each word that is sent, equal to 7 dots.
     
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  10. Neddy Bate Valued Senior Member

    Messages:
    2,408
    I didn't know that either. So there is a rhythm set, and thereby a tempo set, sort of like a drummer in music?
     
  11. DaveC426913 Valued Senior Member

    Messages:
    17,107
    Except that individual letters and words are different lengths so the beats never fall in a pattern. I guess it has a tempo, but not a rhythm.
     

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