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  2. Morse code - Wikipedia

    en.wikipedia.org/wiki/Morse_code

    Morse code. Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called dots and dashes, or dits and dahs. [3] [4] Morse code is named after Samuel Morse, one of the early developers of the system adopted for electrical telegraphy .

  3. SOS - Wikipedia

    en.wikipedia.org/wiki/SOS

    SOS is a Morse code distress signal ( ), used internationally, originally established for maritime use.In formal notation SOS is written with an overscore line (SOS), to indicate that the Morse code equivalents for the individual letters of "SOS" are transmitted as an unbroken sequence of three dots / three dashes / three dots, with no spaces between the letters.

  4. Global Maritime Distress and Safety System - Wikipedia

    en.wikipedia.org/wiki/Global_Maritime_Distress...

    It spelled the end of Morse code communications for all but a few users, such as amateur radio operators. The GMDSS provides for automatic distress alerting and locating in cases where a radio operator does not have time to send an SOS or MAYDAY call, and, for the first time, requires ships to receive broadcasts of maritime safety information ...

  5. Identification friend or foe - Wikipedia

    en.wikipedia.org/wiki/Identification_friend_or_foe

    Identification, friend or foe ( IFF) is a combat identification system designed for command and control. It uses a transponder that listens for an interrogation signal and then sends a response that identifies the broadcaster. IFF systems usually use radar frequencies, but other electromagnetic frequencies, radio or infrared, may be used. [1]

  6. Frequency modulation - Wikipedia

    en.wikipedia.org/wiki/Frequency_modulation

    Frequency modulation ( FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing . In analog frequency modulation, such as radio broadcasting, of an audio signal representing voice or music, the ...

  7. Morse code mnemonics - Wikipedia

    en.wikipedia.org/wiki/Morse_code_mnemonics

    Morse code mnemonics are systems to represent the sound of Morse characters in a way intended to be easy to remember. Since every one of these mnemonics requires a two-step mental translation between sound and character, none of these systems are useful for using manual Morse at practical speeds. Amateur radio clubs can provide resources to ...

  8. American Morse code - Wikipedia

    en.wikipedia.org/wiki/American_Morse_code

    American Morse code. American Morse Code — also known as Railroad Morse—is the latter-day name for the original version of the Morse Code developed in the mid-1840s, by Samuel Morse and Alfred Vail for their electric telegraph. The "American" qualifier was added because, after most of the rest of the world adopted " International Morse Code ...

  9. Reginald Fessenden - Wikipedia

    en.wikipedia.org/wiki/Reginald_Fessenden

    Reginald Aubrey Fessenden (October 6, 1866 – July 22, 1932) was a Canadian-born inventor who received hundreds of patents in various fields, most notably ones related to radio and sonar . Fessenden is best known for his pioneering work developing radio technology, including the foundations of amplitude modulation (AM) radio.