Home > About Us > Press > The Coastline > EPIRBS, PLBS and AIS: Behind The Acronyms

Click to enlarge

EPIRBS, PLBS and AIS: Behind The Acronyms

Use arrows to see more images. Click to Zoom.
One of the greatest advances in marine safety is the ability to quickly summon help in an emergency anywhere in the world. Emergency beacons give us this piece of mind, but the different varieties on the market can land the layperson in a morass of complicated acronyms. Here we are going to try and make sense of EPIRBs, PLBs, and Personal AIS beacons. These are the devices that mariners will typically see available.

The EPIRB (Emergency Position-Indicating Radio Beacon) is a communications device which is used to alert rescue services that a vessel is in distress. As the name indicates these devices use the 406MHz radio frequency to alert the the Search and Rescue Satellite aided Tracking also known as the COSPAS-SARSAT Syetem system. This network of satellites is monitored by NOAA for the purpose of detecting and location those in distress.

When a distress signal is received, NOAA relays relevant information to the US Mission Control Center, who then coordinates with the appropriate rescue authorities. Since NOAA operates the satellites, EPIRB registrations are managed and maintained through their online beacon registration database. EPIRB registration is relative to every boat, meaning if you bring your EPIRB onto a chartered boat or buy a different boat, YOU WILL BE REQUIRED TO ADJUST THE EPIRB REGISTRATION. This avoids false alerts that could put rescue agencies and individuals into harm's way. Additionally, this helps consolidate resources to focus on real distress emergencies.

Many EPIRBs are GPS enabled, meaning they also communicate with the Global Positioning Satellite system to determine the beacon's location. This location data is then transmitted and integrated with COSPAS-SARSAT network to provide improved location accuracy.

EPIRBS are activated in two ways, automatically (Class I) when immersed in water. or manually (Class II). Once activated, an EPIRB will transmit location and distress data for a minimum of 48 hours. As well, EPIRBs float upright in a transmitting position to help ensure data transmission by keeping the antennae above the water surface. Typically one EPIRB per vessel is enough though those headed well offshore may also want to put an additional EPIRB in their ditch bag as a back-up to the primary EPIRB.

EPIRBs do require periodic servicing, which should be performed as per the manufacturer's recommendations. This is mostly because their battery's non-use shelf-life varies between 5 and 7 years. Service periods and frequency will depend on the manufacturer and the individual EPIRB model. Generally a 3-5 year timeframe is recommended. Each EPIRB provides the user with stamped dating to indicate when the EPIRB was manufactured or by which date the EPRIB shall require professional bench testing service, a series of tests provide by a certified servicer. This service typically includes the installation of a new battery.

While there are models coming to the market that enable for end-users to change and replace batteries, it is always recommended to have the periodic bench-testing as this ensures the EPIRB is operating as it was designed.

Take Away: EPIRBs are Registered to an individual vessel, communicates with rescue authorities anywhere in the world, uses satellites, 48 hour battery life, can activate manually, or automatically.

Best Used By: Vessels, especially those traveling off shore should have EPIRBs. If it does not you should re-consider going offshore on that vessel.

A PLB or Personal Locator Beacon, functions similarly to their larger cousins, thus they are sometimes referred to as Personal EPIRBs. Just like their larger brethren, they broadcast their signal on the COSPAS-SARSAT System, and summon help from rescue authorities just like an EPIRB. Unlike en EPIRB they are registered to an individual instead of a vessel, however are be required provide the name of the vessel the PLB will be used on. Thus, if you're crew on multiple boats, you will need to alter your PLB registration accordingly each and every time you sail on a specific boat.

PLBs are significantly smaller, and are designed to be carried on an individual whenever on the water. Many lifejackets have a PLB pocket for easy storage. PLBs haven a shorter battery life than EPIRBS at 24 hours. Also, they must be manually activated and held in a transmitting position.

Take Away: Registered to an individual- yet still require vessel name, communicates to rescue authorities anywhere in the world, 48 hour battery life, must be manually activated and held, small enough to be carried in a lifejacket or pocket at all times.

Best Used By: If you are on the boat alone, or you are only a few miles off shore and don’t have AIS, carry a PLB

Personal AIS
These beacons are very different from previously mentioned. Instead of communicating with rescue authorities through satellites they communicate to vessels in the area with standard VHF radio transition. You may be familiar with AIS (Automatic Identification System) as it was originally developed as a collision avoidance system. Commercial and recreational boats of all sizes use AIS to send and receive data including position, heading and speed. This information shows up on the vessels chart plotter, allowing captain and crew to easily identify and visualize marine traffic around them.

When a personal AIS beacon is activated it broadcasts a standard Man-Overboard alarm as well as position information. Any vessel with AIS in range will receive the information and display a corresponding man overboard icon on the plotter, and sound an alarm. Personal AIS beacons make it easy for the vessel you may have fallen off of to find you and easily provide the greatest chance of survival of a MOB situation as any rescue vessel is within VHF radio range.

The one drawback is that VHF radio range typically runs to the user's horizon line, boats outside of this range are typically unable to receive the signal. Which is why use of the PLB in conjunction with a personal AIS, and good PFD, will provide those who fall overboard the best chance of survival

Take Away: Not registered with NOAA, communicates to AIS enabled vessels in the area via line of sight radio transmission, 24 hour battery life, may some are automatic, some are manual, small enough to be kept in lifejacket, or pocket at all times.

Best Used By: These devices are good for any mariner. Whether or not the vessel you are on has AIS, you should carry a personal AIS beacon because the growing ubiquity of AIS enabled chart-plotters will increase your chances of walking on dry land again.