Editing Distress signal (section)

== Maritime ==
Distress signals at sea are defined in the [[International Regulations for Preventing Collisions at Sea]] and in the [[International Code of Signals]].<ref name="Witherby171">{{cite book | title=COLREGS | publisher=[[Witherby Publishing Group]]| publication-place=Livingston | date=2023 | isbn=978-1-914993-20-6 | page=171}}</ref> [[Mayday]] signals must only be used where there is grave and imminent danger to life. Otherwise, urgent signals such as [[pan-pan]] can be sent. Most jurisdictions have large penalties for false, unwarranted, or prank distress signals. The alerts are of utmost importance in ensuring the safety of life at sea, and are governed by international maritime law, specifically the International Convention for the Safety of Life at Sea (SOLAS).<ref>{{Cite web |title=Distress Alerts |url=https://www.maridict.com/distress_alerts |access-date=2023-11-23 |website=Maritime Dictionary}}</ref>

Distress can be indicated by any of the following officially sanctioned methods:
[[File:Distress Signals.png|thumb|Distress Signals]]
[[File: Smoke signal 1.jpg|thumb|Smoke signal]]

* Transmitting a spoken voice [[Mayday (distress signal)|Mayday]] message by radio over [[very high frequency]] [[Marine VHF radio|channel 16]] (156.8 [[Hertz|MHz]]) or [[medium frequency]] on [[2182 kHz]]<ref name="Witherby171"/>
* Transmitting a digital distress signal by activating (or pressing) the distress button on a marine radio equipped with [[Digital Selective Calling|Digital Selective Calling (DSC)]] over VHF channel 70 or over another designated DSC frequency in the maritime MF and HF bands.<ref name="Witherby171"/>
* Transmitting a digital distress signal by activating (or pressing) the distress button (or key) on an [[Inmarsat-C]] satellite internet device<ref name="Witherby171"/>
* Sending the [[Morse code]] group <span style="text-decoration: overline">[[SOS]]</span> ({{Morse|dot|dot|dot|dash|dash|dash|dot|dot|dot}}) by light flashes or sounds<ref name="Witherby171"/>
* Burning a red [[flare]] (either hand-held or aerial parachute flare)<ref name="Witherby171"/>
* Launching [[distress rocket]]s<ref name="Witherby171"/>
* Emitting orange [[smoke signal|smoke]] from a canister<ref name="Witherby171"/>
* Showing flames on the vessel (as from a burning tar barrel, oil barrel, etc.)<ref name="Witherby171"/>
* Raising and lowering slowly and repeatedly both arms outstretched to each side<ref name="Witherby171"/>
* Making a continuous sound with any [[foghorn|fog-signaling apparatus]]<ref name="Witherby171"/>
* Firing a gun or other explosive signal at intervals of about a minute<ref name="Witherby171"/>
* Flying the [[international maritime signal flags]] '''NC''' [[File:ICS November.svg|20px|border]] [[File:ICS Charlie.svg|20px|border]]<ref name="Witherby171"/>
* Displaying a visual signal consisting of a square flag having above or below it a ball or anything resembling a ball (round or circular in appearance)<ref name="Witherby171"/>

A floating man-overboard pole or dan buoy can be used to indicate that a person is in distress in the water and is ordinarily equipped with a yellow and red flag (international code of signals flag "O") and a flashing lamp or strobe light.

In North America, marine search and rescue agencies in Canada and the United States also recognize certain other distress signals:
* Sea marker dye
* White high-intensity strobe light flashing at 60 times per minute

===Automated radio signals===
In addition, distress can be signaled using automated radio signals such as a [[Search and Rescue Transponder]] (SART) which response to 9&nbsp;GHz radar signal, or an [[Emergency Position-Indicating Radio Beacon]] (EPIRB) which operates in the 406&nbsp;MHz radio frequency. EPIRB signals are received and processed by a constellation of satellites known as [[Cospas-Sarsat]]. Older EPIRBs that use 121.5&nbsp;MHz are obsolete. Many regulators require vessels that proceed offshore to carry an EPIRB.

Many EPIRBs have an in-built Global Positioning System receiver. When activated these EPIRBs rapidly report the latitude and longitude of the emergency accurate to within {{cvt|120|m|ft}}. The position of non-GPS EPIRBs is determined by the orbiting satellites, this can take ninety minutes to five hours after activation and is accurate to within {{cvt|5|km|mi}}. Marine safety authorities recommend the use of GPS-equipped EPIRBs.<ref>{{cite web|title=GPS versus Non-GPS: A comparison of GPS vs non-GPS 406 MHz distress beacons|url=http://beacons.amsa.gov.au/gps.html|publisher=Australian Maritime Safety Authority|access-date=21 March 2014}}</ref>

A miniaturized EPIRB capable of being carried in crew members' clothing is called a Personal Locator Beacon (PLB). Regulators do not view them as a substitute for a vessel's EPIRB. In situations with a high risk of "man overboard", such as open ocean yacht racing, PLBs may be required by the event's organizers. PLBs are also often carried during risky outdoor activities on the land.

EPIRBs and PLBs have a unique identification number (UIN or "HexID"). A purchaser should register their EPIRB or PLB with the national search and rescue authority; this is free in most jurisdictions. EPIRB registration allows the authority to alert searchers of the vessel's name, label, type, size, and paintwork; to promptly notify next-of-kin, and to quickly resolve inadvertent activations.

A DSC radio distress signal can include the position if the lat/long are manually keyed into the radio or if a GPS-derived position is passed electronically directly into the radio.

===Mayday===
A Mayday message consists of the word "mayday" spoken three times in succession, which is the distress signal, followed by the distress message, which should include:
* Name of the vessel or ship in distress
* Its position (actual, last known, or estimated expressed in lat/long or in distance/bearing from a specific location)
* Nature of the vessel distress condition or situation (e.g. on fire, sinking, aground, taking on water, adrift in hazardous waters)
* Number of persons at risk or to be rescued; grave injuries
* Type of assistance needed or being sought
* Any other details to facilitate resolution of the emergency such as actions being taken (e.g. abandoning ship, pumping flood water), estimated available time remaining afloat

=== Unusual or extraordinary appearance ===
When none of the above-described officially sanctioned signals are available, attention for assistance can be attracted by anything that appears unusual or out of the ordinary, such as a [[Jib|jib sail]] hoisted upside down.

During daylight hours when the sun is visible, a [[heliograph]] mirror can be used to flash bright, intense sunlight. Battery-powered laser lights the size of small flashlights (electric torches) are available for use in emergency signaling.

=== Inverted flags ===
For hundreds of years inverted [[national flag]]s were commonly used as distress signals.<ref>For example, 36 [[United States Code|U.S. Code]] [https://web.archive.org/web/20140324220425/http://www.gpo.gov/fdsys/pkg/USCODE-1996-title36/html/USCODE-1996-title36-chap10-sec176.htm §176](a) provides: "The flag should never be displayed with the union down, except as a signal of dire distress in instances of extreme danger to life or property."</ref> However, for some countries' flags it is difficult (e.g., [[Spain]], [[South Korea]], [[United Kingdom]]) or impossible (e.g., [[Japan]], [[Thailand]], and [[Israel]]) to determine whether they are inverted. Other countries have flags that are inverses of each other; for example, the [[Poland|Polish]] flag is white on the top half and red on the bottom, while [[Indonesia]]'s and [[Monaco]]'s flags are the opposite—i.e., top half red, the bottom half white. A ship flying no flags may also be understood to be in distress.<ref>[https://www.pbs.org/wnet/secrets/transcripts/slave-ship-mutiny-program-transcript/755/ "Slave Ship Mutiny Program Transcript"] {{Webarchive|url=https://web.archive.org/web/20101115013507/http://www.pbs.org/wnet/secrets/transcripts/slave-ship-mutiny-program-transcript/755/ |date=15 November 2010 }}. Educational Broadcasting Corporation. 2010. Retrieved 2012-02-15.</ref> For one country, the [[Philippines]], an inverted flag is a symbol of war rather than distress.<ref>{{cite news | url=https://www.reuters.com/article/us-philippines-flag/u-s-apologizes-for-flying-philippine-flag-upside-down-idUSTRE68Q4EE20100927 | title=U.S. Apologizes for flying Philippine flag upside down | newspaper=Reuters | date=27 September 2010 }}</ref>

If any flag is available, distress may be indicated by tying a knot in it and then flying it upside-down, making it into a ''[[wiktionary:wheft|wheft]]''.<ref>{{cite web |url=http://www.allstates-flag.com/fotw/flags/xf-flip.html |title=Flying flags upside down |publisher=Allstates-flag.com |access-date=2009-07-27 |url-status=dead |archive-url=https://web.archive.org/web/20091213230400/http://www.allstates-flag.com/fotw/flags/xf-flip.html |archive-date=2009-12-13 }}</ref>

{{Gallery
 |title=Examples of inverted flags as distress signals
 |align=center
 |File: The Loss of the Romney Man of War.jpg|{{HMS|Romney|1762|6}} aground off the island [[Texel]] in 1804. In Richard Corbould's print, ''Romney''{{'}}s [[blue ensign]] at the stern is shown inverted, as a sign of distress
 |File: HMS Pique in a gale during her return to England RMG BHC2257.jpg|{{HMS|Pique|1834|6}} in a gale, flying the [[white ensign]] upside down
}}

=== Device loss and disposal ===
To avoid pointless searches some devices must be reported when lost. This particularly applies to EPIRBs, lifebuoys, rafts, and devices marked with the vessel's name and port.

Expired flares should not be set off, as this indicates distress. Rather, most port authorities offer disposal facilities for expired distress pyrotechnics. In some areas special training events are organized, where the flares can be used safely.<!--regularly arranged in parts of Finland, in cooperation with emergency authorities-->

EPIRBs must not be disposed of into general waste as discarded EPIRBs often trigger at the waste disposal facility. In 2013, the majority of EPIRB activations investigated by the Australian Maritime Safety Authority were due to the incorrect disposal of obsolete 121.5&nbsp;MHz EPIRB beacons.<ref>{{cite web |last=Gaden |first=Phil |title=A 406Mhz beacon is your best chance of being rescued |url=https://www.youtube.com/watch?v=-X8FJmdcmAI |archive-url=https://web.archive.org/web/20131212014747/http://www.youtube.com/watch?v=-X8FJmdcmAI&gl=US&hl=en |archive-date=2013-12-12 |url-status=dead |publisher=Australian Maritime Safety Authority |access-date=21 March 2014}}</ref>