Editing Emergency position-indicating radiobeacon (section)

== Emergency Position-Indicating Radio Beacon ==
Emergency Position-Indicating Radio Beacons (EPIRBs) are a development of the ELT designed specifically for use on boats and ships, and basic models tend to be less expensive than ELTs (average cost is $800<ref name=":2"/>). As such, instead of using an impact sensor to activate the beacon, they typically use a water-sensing device or a submerged-sensing device that activates and releases a floating beacon after it has been submerged in between 1 and 4 meters of water. In addition to the 406&nbsp;MHz signal mandated by C/S T.001, the IMO and ICAO require an auxiliary 121.5&nbsp;MHz at another frequency in order to support the large installed base of 121.5&nbsp;MHz direction finding equipment.

The [[RTCM]] (Radio Technical Commission for Maritime Services) maintains specifications specific to EPIRB devices. The alarm signal is defined as an AM signal (A3X and/or N0N emissions), containing a swept tone ranging from 1600&nbsp;Hz to 300&nbsp;Hz (either upwards or downwards), with 2-4 sweeps per second.<ref name=":11"/><ref name=":12"/>

EPIRBs with an [[Automatic identification system|AIS]] transmitter are allocated [[Maritime Mobile Service Identity|MMSI]] numbers in the range 974yyzzzz.
[[File:EPIRB sending distress alerts to Search and Rescue.jpg|alt=An EPIRB floating in the water next to distressed boating family in a liferaft|thumb|A GPS-enabled EPIRB transmitter alerts agencies of an emergency, assisting with [[Search and rescue|SAR]] efforts.]]

===EPIRB sub-classification===
Emergency position-indicating radio beacons (EPIRBs) are sub-classified as follows:<ref name="autogenerated1">{{Cite web|url=https://www.navcen.uscg.gov/?pageName=mtEpirb|title=Emergency Position Indicating Radiobeacon (EPIRB)|website=www.navcen.uscg.gov}}</ref>

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

'''Obsolete classes:'''
* Class A – 121.5/243&nbsp;MHz. Float-free, automatically activating. Due to limited signal coverage and possible lengthy delays in signal recognition, the U.S. Coast Guard no longer recommends use of this type. These devices have been phased out by the U.S. [[Federal Communications Commission]] (FCC) and ''are no longer recognized''.
* Class B – 121.5/243&nbsp;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&nbsp;MHz. Similar to Class B, except it floats, or is an integral part of a [[Lifeboat (shipboard)|survival craft (lifeboat)]] or [[survival suit]]. These devices have been phased out by the FCC and ''are no longer recognized''. Their use is no longer recommended by the U.S. Coast Guard.
* Class C – [[Marine VHF radio|Marine VHF]] ch15/16. Manually activated, these beacons operate on maritime channels only, and therefore are not detectable by satellite or normal aircraft. 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. These devices have been phased out by the FCC and ''are no longer recognized''.
* [[Inmarsat-E]] – This entered service in 1997 and service ended 1 December 2006; all former users have switched to Category I or II 406&nbsp;MHz EPIRBs. These beacons were float-free, automatically activated EPIRBs operated on 1646&nbsp;MHz and were detectable by the Inmarsat geostationary satellite system, and were recognized by [[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.<ref>{{cite web|url=http://maritime.inmarsat.com/news/00014622.aspx?language=EN&textonly=False|title=Inmarsat will withdraw epirb service in 2006 and promises new safety service on next generation I-4 satellites|archive-url=https://web.archive.org/web/20061209092859/http://maritime.inmarsat.com/news/00014622.aspx?language=EN&textonly=False|archive-date=December 9, 2006|url-status=dead}}</ref>
* Furthermore, the U.S. Coast Guard recommend that no EPIRB of any type manufactured before 1989 be used.
EPIRBs are a component of the [[Global Maritime Distress and Safety System]] (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&nbsp;MHz frequency processing by satellites, the FCC has prohibited the use of 121.5&nbsp;MHz EPIRBs as of January 1, 2007 (47 CFR 80.1051). See [[National Oceanic and Atmospheric Administration|NOAA]]'s statement [http://www.sarsat.noaa.gov/phaseout.html on the 121.5/243 phaseout] {{Webarchive|url=https://web.archive.org/web/20180209062955/http://www.sarsat.noaa.gov/phaseout.html |date=2018-02-09 }}.

=== EPIRB activation ===
Automatic EPIRBs are water 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 must physically remove it from its bracket or automatically where water pressure will cause a [[hydrostatic]] release unit to separate 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 switch|reed safety switch]] in the EPIRB. This prevents accidental activation if the unit gets wet from rain or turbulent seas.

Once deployed, EPIRBs can be activated, depending on the circumstances, either manually (crewman flicks a switch) or automatically (when water contacts 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."

==== Automatic hydrostatic release unit ====
A '''hydrostatic release unit''' is designed to deploy automatically when submerged to a prescribed depth; the pressure of the water activates a mechanism which releases the EPIRB.
[[File:Epirb hydrostatic release mechanism.jpg|thumb|EPIRB hydrostatic release mechanism]]