An international distress frequency is a radio frequency that is designated for emergency communication by international agreement.

History

For much of the 20th century,

500 kHz From early in the 20th century, the radio frequency of 500 kilohertz (500 kHz) was an international calling and distress frequency for Morse code maritime communication. For much of its early history, this frequency was referred ...

was the primary international distress frequency. Its use has been phased out in favor of the

Global Maritime Distress and Safety System The Global Maritime Distress and Safety System (GMDSS) is a worldwide system for automated emergency signal communication for ships at sea developed by the United Nations' International Maritime Organization (IMO) as part of the SOLAS Convention ...

(GMDSS). Use of some distress frequencies is permitted for calling other stations to establish contact, whereupon the stations move to another frequency. Such channels are known as ''distress, safety and calling frequencies''. Satellite processing from all 121.5 or 243 MHz locators has been discontinued. Since February 1, 2009, the U.S. Coast Guard only monitors distress signals from emergency position indicating radio beacons (

EPIRB An emergency position-indicating radiobeacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats; it is a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in nee ...

s) that broadcast using digital 406 MHz signals. Digital 406 MHz models became the only ones approved for use in both commercial and recreational watercraft worldwide on January 1, 2007.

Maritime Mobile Service frequencies

International distress frequencies, currently in use are: *

2182 kHz 2182 kHz is a radio frequency designed exclusively for distress calls and related calling operations – Mostly historical information for dates prior to February 2009. in the maritime service. It is equivalent to a wavelength of 137.4 ...

for medium range maritime voice use. The US Coast Guard has said "beginning August 1st, 2013 the Coast Guard would no longer monitor 2182 kHz". Many other MRCCs, for example most in Northern Europe, now only have MF capabilities and no HF. * Several HF maritime voice frequencies exist for long-distance distress calls: ** 4125 kHz ** 6215 kHz ** 8291 kHz ** 12290 kHz ** 16420 kHz * Marine VHF radio Channel 16 (156.8 MHz) for short range maritime use * 406 MHz to 406.1 MHz is used by the

Cospas-Sarsat The International Cospas-Sarsat Programme is a satellite-aided search and rescue (SAR) initiative. It is organized as a treaty-based, nonprofit, intergovernmental, humanitarian cooperative of 45 nations and agencies (see infobox). It is dedica ...

international satellite-based

search and rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...

(SAR) distress alert detection and information distribution system

Digital selective calling frequencies

Several maritime frequencies are used for

digital selective calling Digital selective calling (DSC) is a standard for transmitting predefined digital messages via the medium-frequency (MF), high-frequency (HF) and very-high-frequency (VHF) maritime radio systems. It is a core part of the Global Maritime Distres ...

(DSC), and they are also monitored for DSC distress signals: * 2.1875 MHz * 4.2075 MHz * 6.312 MHz * 8.4145 MHz * 12.577 MHz * 16.8045 MHz * 156.525 MHz, Marine VHF radio Channel 70

Aeronautical frequencies

* 121.5 MHz is the civilian

aircraft emergency frequency The aircraft emergency frequency (also known in the USA as Guard) is a frequency used on the aircraft band reserved for emergency communications for aircraft in distress. The frequencies are 121.5 MHz for civilian, also known as International A ...

or ''International Air Distress'' frequency. It is used by some civilian

emergency locator beacon An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to geolocalization, locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons ar ...

s; however, the

system no longer monitors the frequency. * 243 MHz for

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

military aircraft emergency frequencies * 406 MHz to 406.1 MHz is used by the

international satellite-based

(SAR) distress alert detection and information distribution system

Search And Rescue frequencies

* 123.1 MHz – Aeronautical Auxiliary Frequency (International voice for coordinated SAR operations). * 138.78 MHz – U.S. military voice SAR on-the-scene use. This frequency is also used for

direction finding Direction finding (DF), radio direction finding (RDF), or radiogoniometry is the use of radio waves to determine the direction to a radio source. The source may be a cooperating radio transmitter or may be an inadvertent source, a naturall ...

(DF). * 155.160 MHz * 172.5 MHz – U.S. Navy emergency

sonobuoy A sonobuoy (a portmanteau of sonar and buoy) is a small expendable sonar buoy dropped from aircraft or ships for anti-submarine warfare or underwater acoustic research. Sonobuoys are typically around in diameter and long. When floating on t ...

communications and homing use. This frequency is monitored by all U.S. Navy ASW aircraft assigned to a SAR mission. * 282.8 MHz – Joint/combined on-the-scene voice and DF frequency used throughout NATO * 406 MHz / 406.1 MHz – Cospas-Sarsat international satellite-based search and rescue (SAR) distress alert detection and information distribution system *

Emergency position-indicating radiobeacon station An emergency is an urgent, unexpected, and usually dangerous situation that poses an immediate risk to health, life, property, or Natural environment, environment and requires immediate action. Most emergencies require urgent intervention to ...

(EPIRB) *

Search and rescue transponder A search and rescue transponder (SART) is a self-contained, waterproof transponder intended for emergency use at sea. These devices may be either a radar-SART, or a GPS-based AIS-SART (automatic identification system SART). The radar-SART is u ...

(SART) * Survival radio

Amateur radio frequencies

VHF, UHF calling frequencies can also be used to make emergency calls

MF and HF frequencies

* Emergency Centre of Activity (ECOA) frequencies informally established by the

International Amateur Radio Union The International Amateur Radio Union (IARU) is an international confederation of national organisations that allows a forum for common matters of concern to amateur radio operators worldwide, and collectively represents matters to the Internatio ...

regional organizations: * Emergency/Disaster Relief Interoperation Voice Channels of the amateur radio Global ALE High Frequency Network: ** 3791.0 kHz

USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...

** 7185.5 kHz USB ** 10145.5 kHz USB ** 14346.0 kHz USB ** 18117.5 kHz USB ** 21432.5 kHz USB ** 24932.0 kHz USB ** 28312.5 kHz USB

Other frequencies

* Citizens band (CB) radio (not available in all countries) ** Emergency channels 9 (27.065 MHz AM) and 19 (27.185 MHz AM) * GMRS: 462.675 MHz is a UHF mobile distress and road information calling frequency allocated to the

General Mobile Radio Service The General Mobile Radio Service (GMRS) is a land-mobile FM UHF radio service designed for short-range two-way voice communication and authorized under part 95 of the US FCC code. It requires a license in the United States, but some GMRS compa ...

and used throughout Alaska and Canada for emergency communications; sometimes referred to as "Orange Dot" by some transceiver manufacturers who associated a frequency with a color-code for ease of channel coordination, until the creation of the Family Radio Service, in 1996, "GMRS 675" or Channel 6/20 on mobile radios today. Its bandwidth can vary between 12.5, 25 and 50 kHz, and is also allocated to ''Ch. 20'' on 22-channel FRS/GMRS "blister pack" radios. It can have a repeater input frequency of 467.675 MHz, and a tone squelch of 141.3 Hz. After FCC deregulation of simplex FRS/GMRS radios, FRS users may transmit up to 2 watts on the GMRS emergency channel 20 (462.675 MHz) with 141.3 Hz CTCSS, or channel 20-22. * MURS: 151.940 MHz (only available in the United States) * FRS: FRS channel 1: 462.5625 MHz (carrier squelch, no tone or sub-channel), channel 3: 462.6125 MHz and channel 20: 462.6750 MHz (141.3 Hz CTCSS - channel 20, code 22 or channel 20-22). * UHF CB (Australia): Emergency channels 5/35 (476.525/477.275 MHz). Channel 5 is the designated simplex and repeater output emergency channel, while channel 35 is used as the repeater input frequency for duplex operation. UHF CB is only available in Australia and New Zealand. *

PMR446 PMR446 ( Private Mobile Radio, 446 MHz) is a licence-exempt service or UHF CB in the UHF radio frequency band, as personal radio service or citizens band radio, and is available for business and personal use in most countries throughout th ...

(Europe): Channel 1 analog (446.00625 MHz, CTCSS 100.0 Hz, channel 1/12), Channel 8 analog (446.09375 MHz, CTCSS 123.0 Hz, channel 8/18). * PMR446 (Europe): Mountain Rescue Channel 7 analog (446.08125 MHz), CTCSS 85.4 Hz (Channel 7/7 in most radios, not all) * CB245 (Thailand): VHF Citizen Band Channel 1 (245.0000 MHz) and Channel 41 (245.5000 MHz) * CB78 (Thailand): VHF-LOW Citizen Band Channel 41 (78.5000 MHz)

References

{{reflist, refs= {{cite web , url = http://www.navcen.uscg.gov/?pageName=cgcommsCall , title = HF Distress and Safety Watchkeeping Schedule , work = U.S. Coast Guard Navigation Center , publisher = U.S. Coast Guard , access-date = Oct 12, 2011 Distress signals Emergency communication International telecommunications Radio communications