Visits to wild places are often deeply rewarding. But these adventures also entail risks that can occasionally prove life threatening—even for the most experienced outdoors people.

That's where Personal Locator Beacons (PLBs) come in. Available for use in the United States since 2003, this remarkable technology provides a powerful safety net for wilderness travelers. Fortunately, newer models have gotten smaller and less expensive than earlier models.

What Is a Personal Locator Beacon?

A PLB is a portable transmitter capable of sending out a personalized emergency distress signal to a network of orbiting military satellites. These satellites can then relay your information to search-and-rescue teams anywhere in the world.

PLBs have rugged, waterproof plastic housings and are powered by special long-lasting lithium batteries. The models sold by REI are about the size of a TV remote control and weigh about one-half pound or less.

Important: A Personal Locator Beacon should be activated only in situations of grave and imminent danger, and only as a last resort when all means of self-rescue have been exhausted.

Shop REI's selection of personal locator beacons.

The Story Behind PLBs

While PLBs have been available for use in the U.S. since 2003, this powerful technology has been around for decades.

If you have saltwater boating experience, you may be familiar with Emergency Position Indicating Radio Beacons (EPIRBs). These devices, designed exclusively for marine environments, have been in use for several decades and are estimated to have saved nearly 15,000 lives.

PLBs are the land-based equivalents of EPIRBs and utilize the same satellite networks. While the U.S. Coast Guard serves as the point of contact for marine rescues, different states have long handled terrestrial rescues through a variety of organizations. The Federal Communications Commission (FCC) eventually approved PLBs for use because no unified organization for land-based rescues has existed.

To overcome this issue, the FCC, NOAA and the U.S. Air Force teamed up and designated the Air Force Rescue Coordination Center (AFRCC) as the single point of contact for land-based rescues. The AFRCC in turn has established connections and software compatibility with search-and-rescue groups in each state.

How a PLB Works

PLBs transmit signals on internationally recognized distress frequencies. In the U.S., PLBs transmit at 406 MHz (MegaHertz), a frequency monitored by NOAA (National Oceanic and Atmospheric Administration) and the AFRCC.

A PLB communicates with a network of Russian, Canadian, American and French satellites known as COSPAS-SARSAT (SARSAT is an acronym for "Search and Rescue Satellite Aided Tracking").

After receiving your transmission, these satellites "fix" on your location using a Doppler Shift method and relay your information to the AFRCC where search and rescue procedures begin. If you use a GPS-compatible PLB, you can deliver your GPS coordinates very quickly without having to wait for the satellites to determine your position.

Personalized Signal

When you buy a PLB, you must register it with NOAA. When you do so, NOAA will link your essential personal information to a 15-character alpha-numeric code known as a Unique Identifying Number (UIN). When activated, the PLB transmits your UIN to the COSPAS-SARSAT satellites via electronic bursts.

While the electronic bursts provide search-and-rescue units with your location, the UIN tells them personal information such as your name, address, phone number and any medical conditions you may have.

Two Types of PLB Signals

When activated, a PLB sends 2 signals: 406 MHz (which carries the UIN and GPS data to the satellites) and 121.5 MHz, a homing frequency.

If you use a PLB without a GPS, the 406 MHz signal from the satellite will get rescuers to within 2 miles of your position. Then search-and-rescue teams will use a tracking device to home in on the 121.5 MHz frequency. With this type of PLB in the continental U.S., it takes an average of approximately 45 minutes to alert search-and-rescue teams of your position.

If you use a PLB with a GPS interface, the 406 MHz signal will guide rescuers to an area less than 100 meters from your position. At the same time, they will employ a tracking device to home in on the 121.5 MHz frequency put out by the PLB. When using a GPS-compatible PLB in the continental U.S, it takes only 5 minutes to alert search-and- rescue personnel of your position.

Keep in mind that it's always a good idea to have a visual and/or audible distress signal such as a signal mirror, whistle, or a strobe light to help catch search and rescue's attention when they get close. Many PLBs include a built-in LED signal light for this purpose.

How Long Will a PLB Transmit?

A PLB comes equipped with a long-lasting lithium battery. This battery remains dormant until you flip the switch to activate the PLB.

By COSPAS-SARSAT regulations:

• A class 1 heavy-duty battery must be able to transmit at -40°F (-40°C) for 24 hours.
• A class 2 battery must be able to transmit at -20°F (-28.9°C) for 24 hours.

Cold temperatures will shorten a battery's operating time, and the situations above represent worst-case scenarios. For example, at a temperature of 70°F, these batteries will operate for approximately twice as long as they will at very cold temperatures.

When Should I Buy an EPIRB Instead of a PLB?

Larger than PLBs, EPIRBs are designed to automatically right themselves, float and transmit in an upright position. These features are essential in a marine environment, as they allow you to tread water while waiting for rescue.

PLBs are smaller devices that are waterproof and do float, but they're not specifically designed to transmit in water.

Both types of beacons signal the same satellites and give them the same information. Both can be used in a land or marine environment, if needed. However, as a general rule choose a PLB for land travel and an EPIRB when venturing into marine environments.

What about the SPOT Satellite Messenger?

A SPOT satellite messenger is a more recent GPS-based innovation that allows you to send your coordinates and status to family and friends, as well as send calls for help. It relies on commercial satellites rather than the military network used by PLBs. While it's a handy tool for casual hikers and backpackers, a SPOT signal is considerably less powerful than a PLB signal and is not intended for serious mountaineering use. An annual subscription fee is required.

No Subscription Fees

You will not have to pay any recurring fees in order to use a PLB. The satellite and search-and-rescue networks are already in place, ready to serve you should you encounter grave danger in the outdoors. Keep in mind, however, that rescues generally come with significant pricetags.

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