What Is The Difference Between A Personal Locator Beacon and an Automatic Identification System?

Our team undertake lifejacket clinic’s at lifeboat station’s, yacht clubs and harbours from time to time and enjoy chatting to yachtsmen and women about all aspects of maritime safety.  One question which crops up regularly relates to….. “what is the difference between a personal locator beacon and an automatic identification system”…… So, we have put together this blog to simply explain the differences.

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Personal Locator Beacon (PLB)

A PLB is a manually activated device that’s transmit’s a radio signal on the 406 MHz frequency to specific Cospas-Sarsat (international, humanitarian search and rescue system) low-earth orbiting and GPS satellites which detect and locate aviators, mariner’s and land-based users such as hikers or mountain bikers in remote locations in distress. The satellites then relay information, via ground tracking stations and Mission Control Centre’s (MCC), and then onto a rescue co-ordination centre.

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National Maritime Operation’s Centre – Fareham

Where is the UK’s Mission Control Centre?

The designated UK Mission Control Centre (MCC) is the National Maritime Operation’s Centre (NMOC) based at Fareham in Hampshire.  Wherever in the world a UK registered PLB is activated, the Mission Control Centre in the respective country which it is operated will then pass the details to the NMOC for further action and investigation.

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Photo credit: Sarsat

How do PLB’s work?

Most PLB’s are also equipped with GPS receivers, thus being able to calculate and send an accurate location embedded within the beacon’s 406 MHz message. Other PLB’s without GPS rely solely upon the less accurate Doppler principle to establish the beacon’s position. The beacon also transmits a homing signal on VHF, to which Search and Rescue helicopters; and lifeboats can home in on.  PLB’s with GPS receivers can give your exact position (within metres) otherwise  it can take up to 90 minutes to get a fix without GPS.

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What happens when you have purchased a PLB?

Once a PLB unit is purchased, there are no subscription fees and the battery should last, if not used, for 5-6 years.  You must register the PLB with the Marine Coastguard Agency and maintain accurate registration details, including the 24-hour Emergency Point of Contact details. UK Beacon Registry contact details: ukbeacons@mcga.gov.uk Tel: 01326 211569

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PLB’s are Global Maritime Distress Safety System (GMDSS) approved. The Global Maritime Distress and Safety System is the technical, operational and administrative structure for maritime distress and safety communications worldwide.

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How does the Automatic Identification System (AIS) work?

Automatic Identification System (AIS) Man-overboard (MOB) is a personal locator device that works electronically exchanging data with multiple ships and base station’s via VHF.  It is not GMDSS approved or monitored in the UK by the HM Coastguard. It is also limited in range (around 5 miles in open water). An AIS MOB device can be rigged into a lifejacket to activate automically with the inflation of a lifejacket.

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Further useful references

Search and Rescue Satellite Aided Communications

What are the advantages of an EPIRB (Electronic Position Indicating Radio Beacon)

RNLI – PLB’s and EPIRB’s

Acknowledgements

HM Coastguard

RNLI

National Oceanic and Atmospheric Administration


Andy Mills

Thanet RNLI Community Safety Officer Striving to reduce accidental drownings by 50% by 2024 by spreading key safety messages to Thanet communities and its visitors.