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A distress signal, also known as a distress call, is an internationally recognized means for obtaining help.Distress signals are communicated by transmitting radio signals, displaying a visually observable item or illumination, or making a sound audible from a distance.
Mayday is an emergency procedure word used internationally as a distress signal in voice-procedure radio communications.. It is used to signal a life-threatening emergency primarily by aviators and mariners, but in some countries local organizations such as firefighters, police forces, and transportation organizations also use the term.
For much of the 20th century, 500 kHz was the primary international distress frequency. Its use has been phased out in favor of the Global Maritime Distress Safety System. Use of some distress frequencies is permitted for calling other stations to establish contact, whereupon the stations move to another frequency.
Mayday is used internationally as the official SOS/distress call for voice. It means that the caller, their vessel or a person aboard the vessel is in grave and imminent danger, send immediate assistance. This call takes priority over all other calls. [14] The correct format for a Mayday call is as follows:
The first US ship to send a wireless distress call in 1905 simply sent HELP (in both International Morse and American Morse code). [3]: 218 On 7 December 1903, Ludwig Arnson was a wireless operator aboard the liner SS Kroonland when the ship lost a propeller off the Irish coast. His call of CQD brought aid from a British cruiser.
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. [1]
RMS Republic was a steam-powered ocean liner built in 1903 by Harland and Wolff in Belfast, and lost at sea in a collision in 1909 while sailing for the White Star Line.The ship was equipped with a new Marconi wireless telegraphy transmitter, and issued a CQD distress call, resulting in the saving of around 1,500 lives.
2182 kHz is analogous to channel 16 on the marine VHF band, but unlike VHF which is limited to ranges of about 20 to 50 nautical miles (40 to 90 km) depending on antenna height, [3] communications on 2182 kHz and nearby frequencies have a reliable range of around 50 to 100 nautical miles (90 to 190 km) during the day and 150 to 300 nautical miles (280 to 560 km) or sometimes more at night.