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.
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 climbers, 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.
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. This may involve the NMOC tasking search and rescue assets eg lifeboat, helicopter, Coastguard Rescue Team etc to the last location transmitted if in the UK.
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.
The signal transmitted by the distress radio beacon includes a digital message which allows the transmission of encoded data such as the unique identifier for the beacon that transmitted the alert and if the beacon has an integral GPS, the beacon’s position. Otherwise the beacon’s signal may need to be detected by two or three satellites before its position can be sufficiently estimated, therefore it may take longer for Search and Rescue assets to locate the PLB and it’s owner.
Return Link Service PLB’s
Return Link Service PLB’s are being activated during 2020, which is a re-assurance signal back to a new generation of SAR beacons to inform the user that their distress signal and location have been detected. This new capability is unique to the Galileo satellites. A detailed blog explaining this new concept will be posted soon.
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: firstname.lastname@example.org Tel: 01326 211569
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.
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.
AIS is also a requirement for larger pleasure vessels on some European inland waterways. This varies by country and regionally by waterway.
Further useful references
What are the advantages of an EPIRB (Electronic Position Indicating Radio Beacon)
National Oceanic and Atmospheric Administration