Emergency Position-Indicating Radio Beacon

Distress radio beacons, also known as emergency beacons, ELT or EPIRB, are tracking transmitter

Tracking transmitter

A Tracking transmitter broadcasts a radio signal which can be detected by a directional antenna By rotating the antenna one can determine the direction the signal lies in and of course whatever it may be attached to...

s which aid in the detection and location of boat

Boat

A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

s, aircraft

Aircraft

An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

, and people in distress

Emergency

An emergency is a situation that poses an immediate risk to health, life, property or environment. Most emergencies require urgent intervention to prevent a worsening of the situation, although in some situations, mitigation may not be possible and agencies may only be able to offer palliative...

. Strictly, they are radiobeacon

Electric beacon

Electric beacons are a kind of beacon used with direction finding equipment to find ones relative bearing to a known location .The term electric beacon includes radio, infrared and sonar beacons.- Radio beacons :...

s that interface with worldwide offered service of Cospas-Sarsat

Cospas-Sarsat

Cospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons...

, the international satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

system for search and rescue

Search and rescue

Search and rescue 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, mostly based upon terrain considerations...

(SAR). When manually activated, or automatically activated upon immersion, such beacons send out a distress signal

Distress signal

A distress signal is an internationally recognized means for obtaining help. Distress signals take the form of or are commonly made by using radio signals, displaying a visually detected item or illumination, or making an audible sound, from a distance....

. The signals are monitored worldwide and the location of the distress is detected by non-geostationary satellites, and can be located by trilateration

Trilateration

In geometry, trilateration is the process of determinating absolute or relative locations of points by measurement of distances, using the geometry of circles, spheres or triangles. In addition to its interest as a geometric problem, trilateration does have practical applications in surveying and...

in combination with triangulation

Triangulation

In trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...

, respecting the varying quality of the signal received.

In the case of 406 MHz beacons which transmit digital signals, the beacons can be uniquely identified almost instantly (via GEOSAR), and furthermore a GPS or GLONASS

GLONASS

GLONASS , acronym for Globalnaya navigatsionnaya sputnikovaya sistema or Global Navigation Satellite System, is a radio-based satellite navigation system operated for the Russian government by the Russian Space Forces...

position can be encoded

Encoder

An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.-Media:...

into the signal, which provides instantaneous identification of the registered user and its location. Frequently, by using the initial position provided via the satellite system, SAR aircraft and ground search parties can home

Homing

Homing is the process of determining the location of something, sometimes the source of a transmission, and going to it.More specifically, it may refer to:*Infrared homing*Semi-active radar homing*Active radar homing*Acoustic homing*Homing...

in on the distress signals from the beacons and come to the aid of the concerned boat, aircraft, or people.

There are three types of distress radio beacons compatible with the Cospas-Sarsat system:

EPIRBs (emergency position-indicating radio beacons) signal maritime distress.
ELTs (emergency locator transmitters) signal aircraft distress.
PLBs (personal locator beacons) are for personal use and are intended to indicate a person in distress who is away from normal emergency services; e.g., 9-1-1
9-1-1
9-1-1 is the emergency telephone number for the North American Numbering Plan .It is one of eight N11 codes.The use of this number is for emergency circumstances only, and to use it for any other purpose can be a crime.-History:In the earliest days of telephone technology, prior to the...

. They are also used for crewsaving applications in shipping and lifeboats at terrestrial systems. In New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, some police stations and the National Parks and Wildlife Service
National Parks and Wildlife Service (New South Wales)
The National Parks and Wildlife Service is part of the Office of Environment and Heritage - the main government conservation agency in New South Wales, Australia....

, provide personal locator beacons to hikers for no charge.

The basic purpose of distress radiobeacons is to get people rescued within the so-called "golden day" (the first 24 hours following a traumatic event) during which the majority of survivors can usually be saved.

Since the inception of Cospas-Sarsat in 1982, distress radiobeacons have assisted in the rescue of over 28,000 people in more than 7,000 distress situations. In 2009 only, the System provided information which was used to rescue 1,596 persons in 478 distress situations.

General description

Most beacons are brightly colored and waterproof. EPIRBs and ELTs are larger, and would fit in a cube about 30 cm (12 in) on a side, and weigh 2 to 5 kg (4 to 11 lb). PLBs vary in size from cigarette-packet to paperback book and weigh 200 g to 1 kg (½ to 2½ lb). They can be purchased from marine suppliers, aircraft refitters, and (in Australia and the United States) hiking supply stores. The units have a useful life of 10 years, operate across a range of conditions (−40°C

Celsius

Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

/°F

Fahrenheit

Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...

to +40°C/+104°F), and transmit for 24 to 48 hours. As of 2003 the cost ranges from around US$139 to US$3000. The performance and specifications of radiobeacons varies according to cost, as described later in this article.

Classification nomenclature

The three distress radiobeacon types are further classified as follows:

Beacon modes

The most important aspect of a beacon in classification is the mode of transmission. There are two valid transmission modes: digital and analog. Where digital usually has a longer range, analog is more reliable.

Digital mode: 406 MHz beacons

406 MHz beacons transmit bursts of digital distress information to orbiting satellites, and may also contain a small integrated analog (121.5 MHz) homing beacon

Homing beacon

A homing beacon is a radio or acoustic device that allows the user to track a ship, aircraft, an animal, or another individual. Depending on the beacon, the range can be as short as a hundred metres, or, in science fiction, allow for tracking a ship through hyperspace....

. Advanced 406 MHz beacons are capable of transmitting a highly-accurate GPS location within their distress message, thus, the process of distress relief is reduced from "search and rescue

Search and rescue

" to "get to and rescue". Getting to the location nonetheless may be very difficult.

The distress message transmitted by a 406 beacon contains the information such as:

which country the beacon originates from
a unique 15-digit hexadecimal beacon identification code (a "15-hex ID")
the encoded identification of the vessel or aircraft in distress, either as an MMSI value, or as, in the case of an ELT, either the aircraft's registration
Aircraft registration
An aircraft registration is a unique alphanumeric string that identifies a civil aircraft, in similar fashion to a licence plate on an automobile...

or its ICAO 24-bit address (from its Mode-S transponder)
when equipped, a GPS position
whether or not the beacon contains a 121.5 MHz "homer"

The digital distress message generated by the beacon varies according to the above factors and is encoded in 30 hexadecimal

Hexadecimal

In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen...

characters. The unique 15-character digital identity (the 15-hex ID) is hard-coded in the firmware of the beacon.

406 MHz beacon facts

406 MHz beacons transmit for a quarter of a second immediately when turned on, and then transmit a digital burst once every 50 seconds thereafter. Both GEOSAR and LEOSAR satellites monitor these signals.
406 MHz beacons will be the only beacons compatible with the MEOSAR (DASS) system.
406 MHz beacons must be registered (see below).

Hex codes

Example hex codes look like the following: 90127B92922BC022FF103504422535

A bit telling whether the message is short (15 hex digits) or long (30 hex digits) format.
A country code, which lets the worldwide COSPAS/SARSAT central authority identify the national authority responsible for the beacon.
Embedded 15-Hex ID or 15-hex transmitted distress message, for example, 2024F72524FFBFF The hex ID is printed or stamped on the outside of the beacon and is hard-coded into its firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

. The 15-hex ID can only be reprogrammed by certified distress radiobeacon technicians. The national authority uses this number to look up phone numbers and other contact information for the beacon. This is crucial to handle the large number of false alarms generated by beacons.
A location protocol number, and type of location protocol: EPIRB or MMSI, as well as all the data fields of that location protocol. If the beacon is equipped with GPS or GLONASS
GLONASS
GLONASS , acronym for Globalnaya navigatsionnaya sputnikovaya sistema or Global Navigation Satellite System, is a radio-based satellite navigation system operated for the Russian government by the Russian Space Forces...

, a rough (rounded) latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

and longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

giving the beacon's current position. In some aircraft beacons, this data is taken from the aircraft's navigation system.
When a beacon is sold to another country, the purchaser is responsible for having the beacon reprogrammed with a new country code and to register it with his/her nation's beacon registry, and the seller is responsible to de-register the deprecated beacon ID with his/her national beacon registry.
One can use the beacon decoder web page at Cospas-Sarsat to decrypt/extract the 15-hex ID from the 30-hex distress message.

AIS SART

These devices are similar to traditional SAR radar transponders (SART), which additionally include a GPS receiver and a transmitter on VHF AIS

AIS

-As a word:* Ais people, a Native American tribe living on the Treasure coast of Florida, United States which had completely disappeared by the mid-18th Century.*Plural of:** ai ** AI -Medicine:...

channels, so they show up on ship AIS receivers. They are lightweight and can be used to equip inflatable liferafts.

Analog mode: all other beacons

A simple analog siren tone is transmitted continuously until the battery dies.
In the case of 121.5 MHz beacons, the frequency is monitored by most commercial airliners.
The Cospas-Sarsat
Cospas-Sarsat
Cospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons...

system detected this type of beacon—prior to 1 February 2009—when a LEOSAR satellite was in view of both the beacon and an LEOLUT (satellite dish
Satellite dish
A satellite dish is a dish-shaped type of parabolic antenna designed to receive microwaves from communications satellites, which transmit data transmissions or broadcasts, such as satellite television.-Principle of operation:...

). Satellite detection of 121.5 MHz beacons ceased on 1 February 2009 (see below).

Frequency

Distress beacons transmit distress signal

Distress signal

s on the following key frequencies; the frequency used distinguishes the capabilities of the beacon. A recognized beacon can operate on one of the three (currently) Cospas-Sarsat

Cospas-Sarsat

satellite-compatible frequencies. In the past, other frequencies were also used as a part of the search and rescue

Search and rescue

system.

Cospas-Sarsat (satellite) compatible beacon frequencies

406 MHz UHF- carrier wave
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

at 406.025 MHz ± 0.005 MHz
121.5 MHz VHF ± 6 kHz (frequency band protected to ±50 kHz) (Satellite detection ceased on 1 February 2009, but this frequency is still used for short-range location during a search and rescue operation)
243.0 MHz VHF ± 12 kHz (frequency band protected to ± 100 kHz) (prior to 1 February 2009)

Cospas-Sarsat incompatible beacon frequencies

Marine VHF radio
Marine VHF radio
Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...

channels 15/16 - these channels are used only on the obsolete Class C EPIRBs
The obsolete Inmarsat-E beacons transmitted to Inmarsat
Inmarsat
Inmarsat plc is a British satellite telecommunications company, offering global, mobile services. It provides telephony and data services to users worldwide, via portable or mobile terminals which communicate to ground stations through eleven geostationary telecommunications satellites...

satellites on 1646 MHz UHF.

Types

The type of a beacon is determined by the environment for which it was designed to be used:

EPIRBs (Emergency Position Indicating Radio Beacons) signal maritime distress,
ELTs (Emergency Locator Transmitters) signal aircraft distress
PLBs (Personal Locator Beacons) are for personal use and are intended to indicate a person in distress who is away from normal emergency services (i.e., 9-1-1
9-1-1
9-1-1 is the emergency telephone number for the North American Numbering Plan .It is one of eight N11 codes.The use of this number is for emergency circumstances only, and to use it for any other purpose can be a crime.-History:In the earliest days of telephone technology, prior to the...

)

Each type is sub-classified:

EPIRB sub-classification

EPIRBS are sub-classified as follows:

Recognized categories:

Category I - 406/121.5 MHz. Float-free, automatically activated EPIRB. Detectable by satellite anywhere in the world. Recognized by GMDSS.
Category II - 406/121.5 MHz. Similar to Category I, except is manually activated. Some models are also water activated.

Unrecognized classes:

Class A - 121.5/243 MHz. Float-free, automatically activating. These devices have been phased out by the U.S. Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

(FCC) and are no longer recognized.
Class B - 121.5/243 MHz. Manually activated version of Class A. These devices have been phased out by the FCC and are no longer recognized.
Class S - 121.5/243 MHz. Similar to Class B, except it floats, or is an integral part of a survival craft (lifeboat)
Lifeboat (shipboard)
A lifeboat is a small, rigid or inflatable watercraft carried for emergency evacuation in the event of a disaster aboard ship. In the military, a lifeboat may be referred to as a whaleboat, dinghy, or gig. The ship's tenders of cruise ships often double as lifeboats. Recreational sailors sometimes...

. These devices have been phased out by the FCC and are no longer recognized.

Class C - Marine VHF
Marine VHF radio
Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...

ch15/16. Manually activated, these beacons operate on maritime channels only, and therefore are not detectable by satellite or normal aircraft. These devices have been phased out by the FCC and are no longer recognized.

Inmarsat-E - This service ended 1 December 2006; all former users have switched to Category I or II 406 MHz EPIRBS. These beacons were float-free, automatically activated EPIRBs operated on 1646 MHz. They were detectable by Inmarsat geostationary satellites, and were recognized by GMDSS. See Inmarsat-E.

ELT sub-classification

ELTs for aircraft may be classed as follows:

A ELT, automatically ejected
AD ELT, automatic deployable
F ELT, Fixed
AF ELT, automatic fixed
AP ELT, automatic portable
W ELT, water activated
S ELT, survival

Within these classes, an ELT may be either a digital 406 MHz beacon, or an analog beacon (see above).

PLB sub-classification

There are two kinds of PLB:

PLB with GPS input (internal or external)
PLB with no GPS input

All PLBs transmit in digital mode on 406 MHz. Additional information about PLBs can be obtained from the Ultimate PLB FAQ at Equipped to Survive.

Activation methods

There are two ways to activate a beacon:

manually, or
automatically

Automatic EPIRBs are water activated, while automatic ELTs are G-force

G-force

The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...

(impact) activated. Some EPIRBs also deploy; this means that they physically depart from their mounting bracket on the exterior of the vessel (usually by going into the water.)

For a marine EPIRB to begin transmitting a signal (or "activate") it first needs to come out of its bracket (or "deploy"). Deployment can happen either manually—where someone has to physically take it out of its bracket—or automatically—where water pressure will cause a hydrostatic release unit to release the EPIRB from its bracket. If it does not come out of the bracket it will not activate. There is a magnet in the bracket which operates a reed safety switch in the EPIRB. This is to prevent accidental activation when the unit gets wet from rain or shipped seas.

Once deployed, EPIRBs can be activated, depending on the circumstances, either manually (crewman flicks a switch) or automatically (as soon as water comes into contact with the unit's "sea-switch".) All modern EPIRBs provide both methods of activation and deployment and thus are labelled "Manual and Automatic Deployment and Activation."

Advantages and disadvantages of the various beacons

Analog (121.5 MHz) Beacons	406 MHz (Digital) Beacons
SAR response delay	SAR response delay
SAR response to anonymous beacons can be delayed 4–6 hours, and as much as 12 hours.	Resolution or response to registered beacons is very swift. SAR response can be activated within approximately 10 minutes of beacon activation (and GEOSAR detection) if distress is evident. Unregistered beacons can usually be responded to after only 1 LEOSAR satellite pass; after two passes, response is immediate.
False alerts	False alerts
Fewer than 2 in 1000 alerts and 2 in 100 composite alerts are actual distress. The Cospas-Sarsat Cospas-Sarsat Cospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons... system has no way of distinguishing between analog beacons and interference (from set top boxes, etc.) False alerts may result in a long and fruitless search by costly SAR assets, although rescue co-ordination centres typically analyse the circumstances, considering location, movement of the source and confirmatory reports before launching an operation Searches for interference signals and false alerts inhibit SAR assets from being available for real searches	All alerts (100%) come from beacons (analog interference is ignored). Approximately 7 out of 10 false alerts are resolved by a phone or radio call, therefore, SAR resources are not wasted SAR assets are more available for actual distress Persons responsible for causing false alerts can avoid having to pay fines and/or paying the costs of operating SAR assets Follow-up to false activations allows continuous reductions in the number of false alerts
Information transmitted by the beacon	Information transmitted by the beacon
Anonymous siren tone	A unique 15, 22, or 30 digit serial number called a Hex Code Hexadecimal In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen... is transmitted The Hex Code can contain a plethora of information, such as: the Country of beacon registration the identification of the vessel or aircraft in distress, and Identification for aircraft ELTs can be in the form of the aircraft's callsign or its ICAO 24-bit address (from its Mode-S transponder) optionally, position data from onboard navigation equipment (GPS)
Beacon registration information	Beacon registration information
Anonymous beacons cannot be registered	There is no charge to register 406 beacons (see below). Unless otherwise advised, personal information is used exclusively for SAR distress alert resolution purposes Hex Code Hexadecimal In mathematics and computer science, hexadecimal is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F to represent values ten to fifteen... registration is mandatory in most countries of the world Beacons are registered with MCC Mission Control Centre (Cospas-Sarsat) In the field of Search and Rescue, Mission Control Centres are a type of clearinghouse responsible for receiving and distributing distress signal alerts from distress radiobeacons... s who have 24-hour access to registry data, such as: Name of the owner of the beacon Name or callsign of the ship, aircraft, or other vehicle the beacon is associated with Cellular, MMSI, and/or pager numbers, and/or other contact information
Transmission power	Transmission power
0.1 W continuous - weak signal cannot usually penetrate debris or trees	5 W pulse mode - strong pulse reaches the satellites
Potential to be seen by a satellite	Potential to be seen by a satellite
To hear and process an analogue signal, both a LEOSAR and a LEOLUT must be within sight of each other continuously for a sufficient duration (several minutes). The LEOLUT does signal analysis via a dotplot of the signals heard, and the computer looks for a Doppler Doppler effect The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from... shift in the signal to triangulate a position. Second detection is necessary due to false alerts and to resolve position—takes an additional 45–100 minutes before SAR assets can be called	GEOSAR provides nearly-instantaneous coverage 70 degrees north and south of the equator Worldwide coverage via LEOSAR — 6 satellites For 406 signals, LEOSARs do not have to be in sight of a LUT to relay a distress message to Cospas-Sarsat Cospas-Sarsat Cospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons... . Once a 406 signal is detected by a satellite, the satellite will "dump" this data towards Earth (thus to all LUTs) for 24 hours. Future use of GNSS satellites will allow worldwide real-time coverage (MEOSAR)
Location detection	Location detection
Two (roughly) "50% chance" mirror-positions (called the "A-side" for the most likely and the "B-side" for the least likely to be accurate) are generated by Doppler triangulation after the first pass of a LEOSAR Due to false alerts, no reaction can occur based on first pass alert A second pass resolves the ambiguity and resolves the search location to a radius of 20 km Moving targets (usually false alerts) produce interfering anomalies; calculated positions are inaccurate	LEOSAR uses same technique as for analog beacons, but, since beacons are uniquely identified as beacons and have improved frequency stability, response can occur based on first-pass information Doppler-only accuracy is within 5 km (3 mi) — that is, the position is sufficiently accurate for SAR purposes even after only one pass. What's more, the "A-position" (the most likely of the two 'mirror' positions) can be determined valid with 98.5% accuracy after only one satellite pass. This accuracy can be increased to 99.3% using so-called "combined Leo-Geo processing," and this technique also enables accurate positions to be generated with as little as two or three bursts from the beacon (i.e. less than 4 minutes of transmission) and thus greatly increases the chances of being found even if the beacon is ultimately consumed by fire or is otherwise destroyed GPS Position can be encoded into the Hex Code and can be updated real-time via GEOSAR Encoded GPS position accuracy is about 15 m (45 ft), however, the space in the hex message protocol for position information is limited, so transmitted accuracy is approximately +/- 125 metres Increases in accuracy are a significant improvement over analog beacons - from two possible positions within a 20 km (12 mi) radius, to 15m accuracy at one position; an improvement in accuracy of over 2500. The improvements in accuracy are largely responsible for the advent of the phrase "taking the 'search' out of Search and Rescue" LEOSAR Doppler triangulation is less affected by beacon movement due to improved frequency stability In the future, near-instantaneous detection & position triangulation via MEOSAR
Age of technology	Age of technology
121.5 MHz beacons were developed in the late 1960s, when car phones weighed roughly 20 lb (the first ELT TSO Technical Standard Order A Technical Standard Order is a minimum performance standard issued by the United States Federal Aviation Administration for specified materials, parts, processes, and appliances used on civil aircraft. Articles with TSO design approval are eligible for use on the United States type certificated... C91 was written in 1971)	406 MHz beacons use proven, modern technologies reminiscent of those found in modern cell phones.

See also Cospas-Sarsat - Advantages of 406 Beacons and Canada's National Search and Rescue Secretariat—Advantages of 406 Beacons

Although modern systems are significantly superior to older ones, even the oldest systems provide an immense improvement in safety, compared to not having any beacon whatsoever.

Phase-out of 121.5 & 243 beacons

Since 1 February 2009, only 406 MHz beacons are detected by the international Cospas-Sarsat

Cospas-Sarsat

SAR satellite system. This affects all maritime beacons (EPIRBs), all aviation beacons (ELTs) and all personal beacons (PLBs). In other words, Cospas-Sarsat has ceased satellite detection and processing of 121.5/243 MHz beacons. These older beacons are now only detectable by ground-based receivers and aircraft.

121.5 and 243.0 MHz EPIRBs are banned on boats in the United States and in many other jurisdictions. More information about the switch to 406 is available on Cospas-Sarsat's 121.5/243 Phase-Out page.

Despite the switch to 406 MHz, pilots and ground stations are encouraged to continue to monitor for transmissions on the emergency frequencies, as many 406 beacons are also equipped with 121.5 "homers." Furthermore, the 121.5 MHz frequency continues to be used as a voice distress frequency (especially in aviation).

SAR response to various beacons

Emergency beacons operating on 406 MHz transmit a unique 15, 22, or 30 character serial number called a Hex Code. When the beacon is purchased the Hex Code should be registered with the relevant national (or international) authority. Registration provides Search and Rescue agencies with crucial information such as:

phone numbers to call,
a description of the vessel, aircraft, vehicle, or person (in the case of a PLB)
the home port of a vessel or aircraft
any additional information that may be useful to SAR agencies

Registration information allows SAR agencies to start a rescue more quickly. For example, if a shipboard telephone number listed in the registration is unreachable, it could be assumed that a real distress event is occurring. Conversely, the information provides a quick and easy way for the SAR agencies to check and eliminate false alarms (potentially sparing the owner of the beacon significant false alert fines.)

An unregistered 406 beacon still carries some information, such as the manufacturer and serial number of the beacon, and in some cases, an MMSI or aircraft tail number

Tail number

A tail number refers to an identification number painted on an aircraft, frequently on the tail.Tail numbers can represent:* An aircraft registration number * United States military aircraft serials-See also:...

/ICAO 24-bit address. Despite the clear benefits of registration, an unregistered 406 beacon is very substantially better than a 121.5/243.0 beacon; this is because the Hex Code received from a 406 beacon confirms the authenticity of the signal as a real SAR alert.
Beacons operating on 121.5 and/or 243.0 MHz simply transmit an anonymous siren tone, and thus carry no information to SAR agencies. Such beacons implicitly rely on the doppler location detection system, or on terrestrial or aeronautical monitoring of the frequency. In the UK, the Distress and Diversion Cell of the Royal Air Force provides continuous monitoring of 121.5 and 243.0 MHz, with autotriangulation from a network of terrestrial receivers on both frequencies. SAR authorities have no way of knowing whether a 121.5/243.0 MHz signal is actually a SAR signal until they physically deploy to the location and home in on

Direction finding

Direction finding refers to the establishment of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication...

the source (and sound) of the transmission. Since SAR resources are scarce (and expensive), most countries do not deploy the most useful SAR homing assets (aircraft) until ambiguity has been resolved (see doppler).

Responsible agencies

In the U.S., offshore beacons are investigated and victims rescued by the Coast Guard

United States Coast Guard

The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...

. On-shore beacons are investigated by local search and rescue services in Alaska. The Air Force Rescue Coordination Center is charged with land-based emergency signals, usually dispatching volunteer members from The United States Air Force Auxiliary Civil Air Patrol

Civil Air Patrol

Civil Air Patrol is a Congressionally chartered, federally supported, non-profit corporation that serves as the official civilian auxiliary of the United States Air Force . CAP is a volunteer organization with an aviation-minded membership that includes people from all backgrounds, lifestyles, and...

. In the U.S. there are no published notification systems for other locations.

Statutory requirements

In the U.S. (as in most jurisdictions) no special license is required to operate an EPIRB. The following paragraphs define other requirements relating to EPIRBs, ELTs, and PLBs.

Registration

All distress alerting beacons operating on 406 MHz should be registered; all vessels and aircraft operating under International Convention for the Safety of Life at Sea

International Convention for the Safety of Life at Sea

The International Convention for the Safety of Life at Sea is an international maritime safety treaty. The SOLAS Convention in its successive forms is generally regarded as the most important of all international treaties concerning the safety of merchant ships.- History :The first version of the...

(SOLAS) and International Civil Aviation Organization

International Civil Aviation Organization

The International Civil Aviation Organization , pronounced , , is a specialized agency of the United Nations. It codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth...

(ICAO) regulations must register their beacons. Some national administrations (including the United States, Canada, Australia, and the UK) also require registration of 406 MHz beacons.

There is no charge to register 406 MHz beacons.
The U.S. Coast Guard warns that a user's "life may be saved as a result of registered emergency information" because it can respond more quickly to signals from registered beacons.
Unless the national registry authority advises otherwise, personal information contained in a beacon is used exclusively for SAR distress alert resolution purposes.

The Cospas-Sarsat Handbook of Beacon Regulations provides the status of 406 MHz beacon regulations in specific countries and extracts of some international regulations pertaining to 406 MHz beacons.

The following list shows the agencies accepting 406 beacon registrations by country:

United States – NOAA
Canada – Canadian Beacon Registry, CFB Trenton for civil beacons, CMCC for military beacons
Australia – AMSA
the United Kingdom – United Kingdom Maritime and Coastguard Agency (MCA)
Greece – Ministry of Merchant Marine and Hellenic Civil Aviation Authority
International – Cospas-Sarsat International 406 MHz Beacon Registration Database (IBRD)

Aviation (ELTs)

Most general aviation aircraft in the U.S. are required to carry an ELT, depending upon the type or location of operation, while scheduled flights by scheduled air carriers are not. However, in commercial aircraft, a cockpit voice recorder

Cockpit voice recorder

A cockpit voice recorder , often referred to as a "black box", is a flight recorder used to record the audio environment in the flight deck of an aircraft for the purpose of investigation of accidents and incidents...

or flight data recorder

Flight data recorder

A flight data recorder is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters...

must contain an Underwater locator beacon

Underwater locator beacon

An underwater locator beacon or underwater acoustic beacon is a device fitted to aviation flight recorders such as the cockpit voice recorder and flight data recorder. ULBs are also sometimes required to be attached directly to an aircraft fuselage...

.

As per 14 CFR 91.207.a.1, ELTs built according to TSO-C91 (of the type described below as "Traditional ELT, unregistered") have not been permitted for new installations since June 21, 1995; the replacing standard was TSO-C91a. Furthermore, TSO-C91/91a ELTs are being replaced / supplemented by the TSO C126 406 MHz ELT, a far superior unit.

Although monitoring of 121.5 and 243 MHz (Class B) distress signals by satellite ceased in February 2009, the FAA has not mandated a mandatory upgrade of older ELT units to 406 in United States aircraft. Transport Canada has put forward a proposed regulatory requirement that requires upgrade to Canadian registered aircraft to either a 406 MHz ELT or an alternate means system; however, elected officials have overruled the recommendation of Transport Canada for the regulation and have asked for a looser regulation to be drafted by Transport Canada. Recent information indicates Transport Canada may permit private, general aviation flight with only an existing 121.5 ELT if there is a placard visible to all passengers stating to the effect that the aircraft does not comply with international recommendations for the carriage of the 406 MHz emergency alerting device and is not detectable by satellites in the event of a crash.

Marine (EPIRBs)

EPIRBs are a component of the Global Maritime Distress Safety System

Global Maritime Distress Safety System

The Global Maritime Distress and Safety System is an internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships, boats and aircraft....

(GMDSS). Most commercial off-shore working vessels with passengers are required to carry a self-deploying EPIRB, while most in-shore and fresh-water craft are not.

As part of the United States efforts to prepare beacon users for the end of 121.5 MHz frequency processing by satellites, the FCC has prohibited the use of 121.5 MHz EPIRBs as of January 1, 2007 (47 CFR 80.1051). See the United States Coast Guard (USCG) brief on the 121.5/243 Phase-out.

The most current and comprehensive information about EPIRBs is provided by the Equipped To Survive Foundation.

Personal locator beacons (PLBs)

Personal locator beacons operating on 406 MHz must be registered. PLBs should not be used in cases where normal emergency response exists.

EPIRBs (marine)

Current marine EPIRBs are generally divided into three classes; Category I, Category II,
and Class B (or Category B). All of these units can be had for under US$600.

The Category I – type is recommended by the IMO
IMO
The three-letter acronym IMO may refer to:* International Mathematical Olympiad* International Maritime Organization** IMO ship identification number, unique identity numbers issued to seacraft * International Meteorological Organization...

because a float-free bracket will deploy automatically once the vessel sinks and the EPIRB will then be activated automatically by immersion in water in the event of a disaster at sea. These EPIRBs are generally housed in a specially designed bracket on deck and the buoyant beacon is designed to rise to the surface and emit two signals, an emergency homing signal on 121.5 MHz and a digital identification Hex Code on 406 MHz that can be used to almost-immediately alert SAR authorities of the distress of the stricken vessel. Category I EPIRBs used in American waters must be registered with NOAA.

Category II EPIRBs are similar to Category I EPIRBs but are generally manual deployment only. Also like Category I EPIRBs, Category II units must be registered.

Class B EPIRBs, also called Category B or "Mini B", operate a 121.5 MHz homing signal only and are usually manual deployment only units. They are the cheapest units but also the least capable. Since the signal has no identification component, Class B EPIRBs are not registered. Due to their limitations, Class B EPIRBs are slowly being phased out. As the International Cospas-Sarsat
Cospas-Sarsat
Cospas-Sarsat is an international satellite-based search and rescue distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979. It is best known as the system that detects and locates emergency beacons...

program no longer monitors Category B EPIRB signals as of February 1, 2009, this type of beacon will become fully obsolete (see above). Although the U.S. Coast Guard no longer recommends them, they remain in wide use.

ELTs (aircraft)

ELTs used in aircraft are of the following types:

The new 406 MHz TSO-126 ELT is the only type of ELT detected by Cospas-Sarsat after February 1, 2009 (see above).

Types Being Phased Out:

TSO-C91 – 121.5 / 243 MHz unregistered – have not been permitted for new installations since June 21, 1995;
TSO-C91a – 121.5 / 243 MHz unregistered – was the replacing standard; most current aviation ELTs are of this type.

PLBs

All PLBs must have a Hex Code on the body. Persons must register this Hex Code with their national SAR agency. See below for types of PLBs no longer used.

Obsolete EPIRBs

There are also several older types of EPIRB devices which are no longer recommended for use.

Class A - A 121.5 MHz automatic activation unit. Due to limited signal coverage and possible lengthy delays in signal recognition, the U.S. Coast Guard no longer recommends use of this type.

Class C - Operates on VHF channel 15/16. Designed for small crafts operating close to shore, this type was only recognized in the United States. Use of these units was phased out in 1999.

Class S - A 121.5 MHz unit similar to Class B but is often included as an integral part of a lifeboat
Lifeboat (shipboard)
A lifeboat is a small, rigid or inflatable watercraft carried for emergency evacuation in the event of a disaster aboard ship. In the military, a lifeboat may be referred to as a whaleboat, dinghy, or gig. The ship's tenders of cruise ships often double as lifeboats. Recreational sailors sometimes...

or survival suit
Survival suit
An immersion suit, or survival suit , is a special type of waterproof dry suit that protects the wearer from hypothermia from immersion in cold water, after abandoning a sinking or capsized vessel, especially in the open ocean...

. Their use is no longer recommended by the U.S. Coast Guard.

Inmarsat E - entered service in 1997. The unit is an automatic activation unit operating on 1646 MHz and detectable by the Inmarsat geostationary satellite system. This class of EPIRB was approved by the Global Maritime Distress Safety System
Global Maritime Distress Safety System
The Global Maritime Distress and Safety System is an internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships, boats and aircraft....

(GMDSS), but not by the United States. In September 2004, Inmarsat announced that it was terminating its Inmarsat E EPIRB service as of December 2006 due to a lack of interest in the maritime community.

Furthermore, the U.S. Coast Guard recommend that no EPIRB of any type manufactured before 1989 be used.

Obsolete ELTs

Any ELT that is not a 406 MHz ELT with a Hex Code became obsolete February 1, 2009.

Obsolete PLBs

Military forces at one time used 121.5/243.0 MHz beacons such as the "PRQ-501," which had a built-in VHF radio. These are being replaced by modern 406 MHz PLBs.

How they work

All the systems work something like this: A beacon is activated by a crash, a sinking, or manually by survivors. The beacon's transmission is picked up by one or more satellites. The satellite transmits the beacon's signal to its ground control station. The satellite's ground station processes the signals and forwards the data, including approximate location, to a national authority. The national authority forwards the data to a rescuing authority. The rescuing authority uses its own receiving equipment to locate the beacon and makes the rescue or recovery. Once the satellite data is in, it takes less than a minute to forward the data to any signatory nation.

There are several systems in use, with beacons of varying expense, different types of satellites and varying performance. Note that even the oldest systems provide an immense improvement in safety, compared to not having a beacon.

GPS-based, registered

The most modern 406 MHz beacons with GPS (US$ $300+ in 2010) track with a precision of 100 meters in the 70% of the world closest to the equator, and send a serial number so the responsible authority can look up phone numbers to notify the registrator (e.g. next-of-kin) in four minutes.

The GPS system permits stationary, wide-view geosynchronous communications satellites to enhance the doppler position received by low Earth orbit

Low Earth orbit

A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...

satellites. EPIRB beacons with built-in GPS are usually called GPIRBs, for GPS Position-Indicating Radio Beacon or Global Position-Indicating Radio Beacon.

However, rescue cannot begin until a doppler track is available.
The COSPAS-SARSAT specifications say

that a beacon location is not considered "resolved" unless at least two doppler tracks match or a doppler track confirms an encoded (GPS) track. One or more GPS tracks are not sufficient.

High-precision registered

An intermediate technology 406 MHz beacon (now mostly obsolete in favor of GPS enabled units) has worldwide coverage, locates within 2 km (12.5 km² search area), notifies kin and rescuers in 2 hours maximum (46 min average), and has a serial number to look up phone numbers, etc. This can take up to two hours because it has to use moving weather satellites to locate the beacon. To help locate the beacon, the beacon's frequency is controlled to 2 parts per billion, and its power is a hefty five watts.

Both of the above types of beacons usually include an auxiliary 25 milliwatt beacon at 121.5 MHz to guide rescue aircraft.

Traditional ELT, unregistered

The oldest, cheapest (US$ 139) beacons sent an anonymous warble at 121.5 MHz. They are no longer monitored by satellite. They could be detected by satellite over only 60% of the earth, required up to 6 hours for notification, located within 20 km (12 mi) (search area of 1200 km²) and were anonymous. Coverage was partial because the satellite had to be in view of both the beacon and a ground station at the same time—the satellites did not store and forward the beacon's position. Coverage in polar and south-hemisphere areas was poor. The frequency was the standard aviation emergency frequency, and there is interference from other electronic and electrical systems, so false alarms were common. To reduce false alarms, a beacon was confirmed by a second satellite pass, which could easily slow confirmation of a 'case' of distress to up to about 4 hours (although in rare circumstances the satellites could be position such that immediate detection becomes possible.) Also, the beacons couldn't be located as well because their frequency is only accurate to 50 parts per million, and they send only 75-100 milliwatts of power.

Location by Doppler (without GPS)

The Cospas-Sarsat system was made possible by Doppler

Doppler effect

The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...

processing. Local unit terminals (LUTs) detecting non-geostationary satellites interpret the Doppler

Doppler effect

frequency shift heard by LEOSAR and MEOSAR satellites as they pass over a beacon transmitting at a fixed frequency. The interpretation determines both bearing and range. The range and bearing are measured from the rate of change of the heard frequency, which varies both according to the path of the satellite in space and the rotation of the earth. This triangulates the position of the beacon. A faster change in the doppler indicates that the beacon is closer to the satellite's ground track. If the beacon is moving toward or away from the satellite track due to the Earth's rotation, it is on one side or other of the satellite's path.

If the beacon's frequency is more precise, it can be located more precisely, saving search time, so modern 406 MHz beacons are accurate to 2 parts per billion, giving a search area of only 2 square km, compared to the older beacons accurate to 50 parts per million that had 200 square kilometers of search area.

In order to increase the useful power, and handle multiple simultaneous beacons, modern 406 MHz beacons transmit in bursts, and remain silent for about 50 seconds.

Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

developed the original system, and its success drove the desire to develop the improved 406 MHz system. The original system was a brilliant adaptation to the low quality beacons, originally designed to aid air searches. It used just a simple, lightweight transponder on the satellite, with no digital recorders or other complexities. Ground stations listened to each satellite as long as it was above the horizon. Doppler shift was used to locate the beacon(s). Multiple beacons were separated when a computer program analysed the signals with a fast fourier transform

Fast Fourier transform

A fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform and its inverse. "The FFT has been called the most important numerical algorithm of our lifetime ." There are many distinct FFT algorithms involving a wide range of mathematics, from simple...

. Also, two satellite passes per beacon were used. This eliminated false alarms by using two measurements to verify the beacon's location from two different bearings. This prevented false alarms from VHF channels that affected a single satellite. Regrettably, the second satellite pass almost doubled the average time before notification of the rescuing authority. However, the notification time was much less than a day.

Operational testing

According to the U.S. Federal Aviation Administration

Federal Aviation Administration

The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...

, ground testing of type A, B and S ELTs is to be done within the first 5 minutes of each hour. Testing is restricted to 3 audio sweeps. http://www.faa.gov/air_traffic/publications/atpubs/ATC/atc1002.html
Type I and II devices (those transmitting at 406 MHz) have a self test function and must not be activated except in an actual emergency.

The United States Coast Guard

United States Coast Guard

web page for EPIRBs states: "You may be fined for false activation of an unregistered EPIRB. The U.S. Coast Guard routinely refers cases involving the non-distress activation of an EPIRB (e.g., as a hoax, through gross negligence, carelessness or improper storage and handling) to the Federal Communications Commission. The FCC will prosecute cases based upon evidence provided by the Coast Guard, and will issue warning letters or notices of apparent liability for fines up to $10,000."

Satellites used

Receivers are auxiliary systems mounted on several types of satellites. This substantially reduces the program's cost.

The weather satellites that carry the SARSAT receivers are in "ball of yarn" orbits, inclined at 99 degrees. The longest period that all satellites can be out of line-of-sight of a beacon is about two hours.

The first satellite constellation was launched in the early 1970s by the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

and the USA.

Some geosynchronous satellites have beacon receivers. Since end of 2003 there are four such geostationary satellites (GEOSAR) that cover more than 80% of the surface of the earth. As with all geosynchronous satellites, they are located above the equator. The GEOSAR satellites do not cover the polar caps.

Since they see the Earth as a whole, they see the beacon immediately, but have no motion, and thus no doppler frequency shift to locate it. However, if the beacon transmits GPS data, the geosynchronous satellites give nearly instantaneous response.

History

The original impetus for the program in the U.S. was the loss of Congressmen

United States House of Representatives

The United States House of Representatives is one of the two Houses of the United States Congress, the bicameral legislature which also includes the Senate.The composition and powers of the House are established in Article One of the Constitution...

Hale Boggs

Thomas Hale Boggs Sr. , was an American Democratic politician and a member of the U.S. House of Representatives from New Orleans, Louisiana...

(D-LA) and Nick Begich

Nick Begich

Nicholas Joseph "Nick" Begich, Sr. was a Democratic Party member of the United States House of Representatives from Alaska. He disappeared in a plane crash in Alaska in 1972. His son Mark Begich is currently the junior U.S...

(D-AK) in the Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

n wilderness on October 16, 1972. A massive search effort failed to locate them. The result was a U.S. law mandating that all aircraft carry an emergency locator transmitter. Technical and organizational improvements followed.

Cospas-Sarsat

Cospas-Sarsat

is an international organization that has been a model of international cooperation, even during the Cold War

Cold War

The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

. SARSAT means Search And Rescue Satellite Aided Tracking.
COSPAS (КОСПАС) is an acronym

Acronym and initialism

Acronyms and initialisms are abbreviations formed from the initial components in a phrase or a word. These components may be individual letters or parts of words . There is no universal agreement on the precise definition of the various terms , nor on written usage...

for the Russian words "Cosmicheskaya Sistema Poiska Avariynyh Sudov" (Космическая Система Поиска Аварийных Судов), which translates to "Space System for the Search of Vessels in Distress". A consortium of Russia, the U.S., Canada and France formed the organization in 1982. Since then 29 others have joined.

Cospas-Sarsat defines standards for beacons, auxiliary equipment to be mounted on conforming weather and communication satellites, ground stations, and communications methods. The satellites communicate the beacon data to their ground stations, which forward it to main control centers of each nation that can initiate a rescue effort.

The U.S. Coast Guard once promoted an emergency beacon on maritime VHF

Marine VHF radio

Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...

emergency channels. It now promotes the superior Cospas-Sarsat system, and no longer services emergency beacons on maritime VHF frequencies.

Current events

In a Safety Recommendation released September 2007, the U.S. National Transportation Safety Board

National Transportation Safety Board

The National Transportation Safety Board is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incidents, certain types of highway crashes, ship and marine...

once again recommended that the U.S. FAA require all aircraft have 406 MHz ELTs. They first recommended this back in 2000 and after vigorous opposition by AOPA

Aircraft Owners and Pilots Association

The Aircraft Owners and Pilots Association is a Frederick, Maryland-based non-profit political organization. Incorporated on 15 May 1939, AOPA's membership consists mainly of general aviation pilots in the United States...

, the FAA declined to do so. This recommendation is apparently a reaction to the cessation of 121.5 MHz satellite processing. Citing two recent accidents, one with a 121.5 MHz ELT and one with a 406 MHz ELT, the NTSB concludes that switching all ELTs to 406 MHz is a necessary goal to work towards.

Alternate technologies

There are also other personal devices in the marketplace which do not meet the standard for 406 MHz devices.

GPS Aircraft Tracking

Active Aircraft Tracking

There are several active aircraft tracking systems available on the market that use the "bread-crumb approach" to SAR. Rather than relying on an emergency locator transmitter to transmit upon impact (which fails to activate in 75% of crashes), the next generation of emergency locating devices are active tracking devices that send position reports at regular time intervals. If the unit stops transmitting upon impact, the historical transmissions will give the last known location of the aircraft, its speed, direction and altitude. Tracking as an alternative or complement to current technology has recently been encouraged by the Coroner in New Zealand.

SPOT

SPOT does not use the 406 MHz signal nor the system of satellites. Instead, it depends on the GlobalStar

Globalstar

Globalstar is a low Earth orbit satellite constellation for satellite phone and low-speed data communications, somewhat similar to the Iridium satellite constellation and Orbcomm satellite systems.-History:...

satellite system. It has richer features (for instance, can send many non-emergency signals) – but it does not work in as many places as 406 MHz PLBs – for instance under dense forest canopy or steep canyons. When a user presses the "911" button on a SPOT device an emergency message containing the unit's identification and GPS location is transmitted to the GEOS International Emergency Response Center who then notifies the appropriate emergency agency for the region after first calling the user to ensure the transmission is not accidental.

SPOT additionally has the ability to provide non-emergency web based tracking information. This allows family or friends at home to track the holder's progress. The tracking operates by sending a tracking signal to the GlobalStar

Globalstar

network every 10 minutes. This feature can additionally be useful to provide location of an individual even if the individual is unable to activate the emergency '911' button.

Typical costs are $169 plus a $99/year service fee for basic services or $150/yr for basic services and tracking services, as compared to around $250 for a 406-MHz PLB with no service fee.

Spidertracks
inReach

inReach, like SPOT does not use the 406 MHz signal nor the system of satellites. Instead, it depends on the Iridium

Iridium

Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...

satellite system. Unlike SPOT inReach is a two way system capable of receiving confirmation that the message was received. Like SPOT the message is transmitted to the private GEOS International Emergency Response Center who then notifies the appropriate SAR authorities.

inReach also provides tracking capability and two way SMS type text messaging allowing family and friends to track and send and receive updates from the trail. Pricing starts at USD$9.95/mo with all messages pay as you go to USD$44.95 per month for unlimited tracking and a message bundle.

TracMe

TracMe simply beacons an automated message on a short-range FRS or UHF CB frequency. It does not notify authorities that you are missing. TracMe's website recommends you arrange for rescue by notifying a friend about your plans, and ask them to call authorities and inform them of your general whereabouts and that you have a TracMe if you are late returning. Then, the search-and-rescue team will need to radio-triangulate on the signal.

TracMe has had a dispute with the FCC whether the device can be called a "Personal Locator Beacon".

The company lists it at a cost of $49.95 and it allows a single use. The company also promises a free replacement if it's used for a genuine emergency.

APRS

Automatic Position Reporting System

Automatic Packet Reporting System is an amateur radio-based system for real time tactical digital communications of information of immediate value in the local area. In addition, all such data is ingested into the APRS Internet system and distributed globally for ubiquitous and immediate access...

is used by amateur radio operators to track positions and send short messages. Most APRS packets contain a GPS latitude and longitude, so they can be used for both normal and emergency tracking. They also are routed to the internet, where they are archived for some period of time, and viewable by others There are several Emergency packet types that can indicate distress. Since it is part of the amateur radio service, it costs nothing to transmit on and uses the extensive network, however, one must be a licensed amateur radio operator. There is also no guarantee that an APRS distress packet report would be seen or handled by emergency responders. It would have to be seen by an amateur radio operator and forwarded on.

External links

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