The Personal Locator Beacon PLB Guide

How Do Personal Locator Beacons Work?

3500539_blogThough our first post, What is a PLB, introduced the uninitiated to the concept of Personal Locator Beacons, it was left intentionally vague. We didn’t want to confuse anybody with technical jargon. Consider it the “what am I buying my kid for Christmas” explanation. This post, however, will delve a bit deeper for those of you in the market for a PLB who want to really understand what you’re getting and are wondering how does a plb work.

As already stated, a personal locator beacon is a portable distress beacon that transmits an emergency signal to rescuers to let them know you are in desperate need of help. That’s a key statement, there. You don’t want to deploy search and rescue teams unless you really have run out of options and you’ve reached a point where failure to get assistance will result in serious injury or loss of life. These are, and should always be thought of, as life saving devices. Use them accordingly.

Personal locator beacons have been around for some time but have only found acceptance (in the US) for personal use since 2003. The United States came a bit late to the game here thanks to resistance from several government entities and at the cost of dozens of lives. Rather than dwell on what could have been, though, we can be thankful that these are now accepted (albeit controversy inspiring) survival tools available at the outdoorsman’s discretion. We’ll get into why there’s controversy associated with them in a later post.

PLBs work by transmitting a 406Mhz (SEE IMPORTANT NOTE AT THE END OF THIS POST) signal monitored by reputable agencies the world over to a network of 4 polar low earth orbit and 3 geostationary operational environmental satellites (at the time of this writing) internationally owned and monitored (American, Canadian, Russian and French). The tracking system is collectively known as COSPAS-SARSAT and membership/monitoring responsibility has expanded to include 36 other nations operating 66 ground stations and 29 mission control centers worldwide (according to NOAA’s SARSAT website). In the US, the 406MHz distress frequency is monitored by NOAA and the Air Force Rescue Coordination Center, the US’ inland search and rescue coordinator responsible for coordinating on-land federal SAR (search and rescue) activities.

Perhaps a bit over-technical but still potentially of interest to some of you reading is that the SARSAT satellites are the NOAA Polar Orbiting Environmental Satellites (POES) and the Russian Nadezhda Satellites are known collectively as COSPAS. The geostationary satellites are NOAA’s Geostationary Orbiting Environmental Satellites (GOES), ISRO – Indian National Satellite (INSAT) and ESA Metosat Second Generation (MSG). Visit for more on these.

Different Kinds of Emergency Locator Beacons

While this blog is devoted to PLBs (personal locator beacons) there are actually 3 types of emergency distress beacons. They are EPIRBs, ELTs and PLBs. The first two are for maritime and aviation use respectively and fall outside the scope of this site. I’ll consider developing additional blogs around them, but for now we’re focusing specifically on PLBs. However, regardless which type of distress beacon you use, the actually process of calling for help and having it delivered is pretty much the same.

On activation, the distress beacon transmits a signal to the orbiting search and rescue satellites comprising the COSPAS-SARSAT collection. The signal is then transmitted to an unmanned ground station known as a Local User Terminal (LUT). That’s a bit of a misrepresentation because LUTs are completely unmanned. There’s no user sitting at any terminal as the name might imply.

The LUT transfers the distress signal to the relevant Mission Control Center (MCC) which, in turn will activate search and rescue by notifying a Rescue Coordination Center. That’s a bit understated because the type of distress beacon received determines precisely who the MCC will notify. In the US, for a personal locator beacon, rescue efforts will be coordinated by the Air Force Rescue Coordination Center. Emergency beacons from EPIRB’s (marine distress beacons) are directed to a Coast Guard RCC.

What Information Does My PLB Provide to Search And Rescue Services?

Most important, the signal from your PLB simply tells rescuers that you are in need of help. That’s really at the heart of the matter. If your beacon isn’t transmitting to the satellites, it’s assumed you’re fine. If it is transmitting, it’s assumed you’re in serious trouble. But modern personal locator beacons actually reveal more.

In your hunt for a personal locator beacon you may often find the abbreviation GPS associated with the units you are considering. Yes, it’s the same acronym (Global Positioning System) you find on the unit in your car but don’t mistake them as interchangeable. Remember that circumstances requiring the use of a PLB are often dire and can involve injury and panic. As such, these systems are designed to be as simple as possible. In association with personal locator beacons, GPS simply refers to the ability of the unit to transmit your latitude and longitude position to rescuers when activated. These units will NOT help you find the nearest Starbucks in time for a desperate coffee fix, but they will narrow your position down for search and rescue teams to within 100 meters. It’s important you know that not all PLBs offer this feature. Instead, signal triangulation will guide rescuers for devices which do not offer a GPS feature.

Your PLB will also require registration for activation. Your registration number is transmitted along with the signal and that helps SAR identify who you are. Some PLBs come with subscription services that open up a whole array of additional options to you. Think of them as concierge services that can include any number of features such as contact between the company and individuals on your emergency contact list. At the heart of it all, these services are incidental and non-essential. The objective of a PLB, after all, is to get you rescued. But they can offer peace of mind to families. Remember that these services are independent of the RCC conducting the actual rescue activity and are managed by the company or subcontractor servicing the particular PLBs subscription.

I think that about covers the fundamentals. From a user perspective, all you really need to know is that if your personal locator beacon is transmitting, rescue efforts are being coordinated. There’s more to these devices worth discussing and we’ll cover them in subsequent posts discussing features, services and responsible use, but for now you should have a pretty good idea of how PLBs work.

IMPORTANT NOTE: As of February 1, 2009 Cospas-Sarsat ceased coverage of the 121.5 MHz and 243 MHz emergency beacons. For more information, visit

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