Comparison of EPIRBs and ELTs

Comparison of different types of EPIRBs:

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EPIRB is an unprotected abbreviation. The abbreviation EPIRB stands for Emergency Position Indicating Radio Beacon. Therefore the incorporation of a position finding device (GPS) is mandatory. The 406-MHz-, the 1,6-GHz- and the DSC-type system definitions allow for position coding within the transmitted message. But only the Inmarsat-E-Type 1,6-GHz-EPIRBs makes use of this feature. Unfortunately, most 406-MHz-beacons lack this feature. The following tables compare features and technical data of different beacons.
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In recent time discount suppliers are misusing the term EPIRB to sell simple 121,5-MHz-beacons (PLT/ELT). The customer should be aware of cheap offers which never provide for a beacon capable of transmitting its identification. Cheap beacons (PLT/ELT) sold as "EPIRBs" never incorporate position finding devices, either.The financial benefit severely bribes the genuine security capabilities of the device.

**Comparison of EPIRBs by their features :**
(Click here for technical data or get an explanation of the abbreviations)
Feature	ELT / PLT (121.5 MHz)	EPIRB (406 MHz)	EPIRB (1.6 GHz, Inmarsat-E)	DSC-EPIRB^***	SART
permitted, recommended or optional features	none	Strobe-Light, ELT	Strobe-Light, ELT, SART	Strobe-Light, SART	Strobe-Light
Vehicle- Identifikation	no	yes	yes	yes	no
is received and processed by ...	COSPAS / SARSAT, planes and SAR-forces	COSPAS / SARSAT (LEO satellites)	Inmarsat, (geostationary satellites)	costal radio stations	vessels within visibility
transmission of the nature of distress	no	possible, not used	possible with RCU, strongly recommended	possible	no
coverage	the whole world	the whole world	97% of the earth, up to ± 80° lattitude (excluding polecaps)	sea-area A1, only in the vincinity of the coast	-
period until valid reception	up to two hours	up to two hours	within 3-10 min **	immediately, no delay	-
minimal mandatory time of operation	-	24 h	75 min TX within 48 h	48 h	96 h stby 8 h TX
specifications to apply	IEC, IMO GMDSS-Handbook	IMO GMDSS-Handbook	Inmarsat SDM 2.0, IMO-GMDSS-Handbook IEC1097-5 ETSI 300 372	IMO GMDSS-Handbook	GMDSS-Handbook

** = Inmarsat calls for a delay of 2-8 minutes after activation. Processing the signals within the LES takes about less than a minute.
*** = For the time beeing, there are no DSC-EPIRBs available on the word market.

Technical data of different EPIRBs :

Feature ELT / PLT
(121.5 MHz) EPIRB
(406 MHz) EPIRB
(1.6 GHz, INMARSAT-E) DSC-EPIRB SART

position-transmission, measurement thru SAT and/or SAR-vehicules thru SAT yes, own position determination possible,
own position determination none ! Position determination by receiving vessel

Type of position-processing Doppler-shift because of SAT-movement, or VHF-direction finder Doppler-shift because of SAT-movement GPS or navigation system of the vessel navigation system of the vessel or GPS none

frequencies 121,5 MHz
(sometimes 243 MHz) 406.025 MHz 667 channels
(300 Hz spacing) at 1,645 GHz VHF CH 70
(156.525 MHz) 9.2 - 9.5 GHz

Type of modulation Carrier keying
(A1 / A1A) PSK, NRZ
± 1.1 rad
(G1B) FSK ± 120 Hz,
NRZ (G2B) FSK,
300 / 2100 Hz,
h=2 (G2B) carrier keying
100 ms
(A0 / A1)

Datarate (Baud) - 400 32 1200 -

Bit per transmission 1 135 160 variable -

Polarisation vertical RHCP RHCP vertical horizontal

transmission power no recommendations 5 W 1 W 100 mW 400 mW

temperature range - -20 ° to 55 ° -20 ° bis 55 ° -20 ° to 55 ° -20 ° to 55 °

Abbreviations :

COSPAS Cosmicheskaya Sistyema Poiska Ava riynich Sudov
(= Space System for the Search of Vessels in Distress), comparison with Inmarsat-E.

DSC Digital Selective Calling

ELT Emergency Locator Transmitter (121,5 MHz Baken-Sender)

EPIRB Emergency Position Indicating Radio Beacon (406 MHz oder 1,6 GHz Notsender)

GMDSS Global Maritime Distress and Safety System

LES Land Earth Station, Receiving Satation for Satellite-Signals (picture)

LEO Low Earth Orbit

MMSI Maritime Mobile Service Identity,
like a ships telephone number in the maritime radio, (VHF, SW und MW)

PLB Personal Locator Beacon (121,5 MHz Baken-Sender, am Körper zu tragen)

SAR Search and Rescue (Rettungsdienst)

SARSAT Search and Rescue Satellite, comparison with Inmarsat-E.

SART Search and Rescue Radar Transponder

SOLAS Safety of Life at Sea, Rules for the Equipment of ships > 300 grt

RCU Remote Control Unit, enter nature of distress and remote activate the EPIRB from the ships bridge. For a picture click here.

RHCP Right Hand Circular Polarisation

SAT Satellit

IMO International Maritime Organisation

GPS Global Positioning System (Satellitennavigationssystem)

VHF Very High Frequency

COSPAS	Cosmicheskaya Sistyema Poiska Ava riynich Sudov (= Space System for the Search of Vessels in Distress), comparison with Inmarsat-E.
DSC	Digital Selective Calling
ELT	Emergency Locator Transmitter (121,5 MHz Baken-Sender)
EPIRB	Emergency Position Indicating Radio Beacon (406 MHz oder 1,6 GHz Notsender)
GMDSS	Global Maritime Distress and Safety System
LES	Land Earth Station, Receiving Satation for Satellite-Signals (picture)
LEO	Low Earth Orbit
MMSI	Maritime Mobile Service Identity, like a ships telephone number in the maritime radio, (VHF, SW und MW)
PLB	Personal Locator Beacon (121,5 MHz Baken-Sender, am Körper zu tragen)
SAR	Search and Rescue (Rettungsdienst)
SARSAT	Search and Rescue Satellite, comparison with Inmarsat-E.
SART	Search and Rescue Radar Transponder
SOLAS	Safety of Life at Sea, Rules for the Equipment of ships > 300 grt
RCU	Remote Control Unit, enter nature of distress and remote activate the EPIRB from the ships bridge. For a picture click here.
RHCP	Right Hand Circular Polarisation
SAT	Satellit
IMO	International Maritime Organisation
GPS	Global Positioning System (Satellitennavigationssystem)
VHF	Very High Frequency