Imagine that you are alone, on one of your usual jaunts exploring a new area and decide to push farther the plan you shared with friends when departing. At the end of a three-hour climb you stand to survey the crests of distant mountains, where your journey began, and the rocks shift under your feet casting you down a steep incline. At the bottom, you collect your senses and do a quick inventory. A stabbing pain in your back sends a terrible message to your brain. You are unable to walk, miles from help and since you altered your plans, no one knows where you are!

Panic doesn't set in until you pull out your cell phone and find that in addition to leaving civilization in your wake, you also put several miles between your phone and the illusive limits of cellular service.

I know what you're thinking. "I'm an experienced outdoorsman, right, that won't happen to me." The facts would belie that attitude, and in reality it's usually the highly experienced that find themselves in a pickle without the prerequisite picnic. Experienced woodsmen are more likely to push the envelope, and to become lax in attention to common tasks that the neophyte would plod through slowly. Take for example the tale of John O'Rourke who was hunting with a group of well-seasoned elk hunters.

One of a group of five veteran Idaho elk hunters had downed a big bull late in the afternoon and returned to gather his companions to assist in the quartering and packing the animal out. Since the bull was confirmed dead, it was decided that the shooter that bagged him would begin the skinning and quartering project while the other four companions hunted the surrounding ridge for the possibility of another elk.

Failing to find any, they all rendezvoused to assist in the skinning. Only minutes after their arrival, as they were taking off their own gear to pitch in, this veteran who had personally shot and skinned over 20 elk suddenly slipped on a forceful cut and impaled a four-inch blade into his thigh, all the way to the hilt.

Fortunately, John had a first aid kit and the presence of mind to use it properly. With the addition of material from a clean, unused game bag, a tourniquet was quickly fashioned, but lacking communications the only option was to walk out. With a makeshift crutch, cut from a sapling aspen, they hobbled down the mountain.

At the hospital, the attending physician determined that the stab wound had only missed the femoral artery by two millimeters. Twenty stitches later, and a bit more experienced in medical procedures than they had desired, this fortunate five-some of hunters returned to the woods extremely conscious of the dire consequences they could have faced.

A PLB could be pulled from a pack, antenna extended, and rescue workers dispatched in a matter of minutes, through an elaborate satellite and ground communications network. A PLB is a pocket-sized, handheld transmitter that sends out a 406 MHz distress signal directly to satellites in low-earth polar and geosynchronous orbits. A five watt digital burst of approximately 0.5 seconds duration approximately every 50 seconds is transmitted randomly between 47.5 to 52.5 seconds to prevent multiple beacon transmissions from interfering with each other.

Once the signal is received it is then relayed through a variety of means to authorities for response. On the ground, Receiving Stations, also called Local User Terminals (LUTs), Mission Control Centers (MCCs), and Rescue Coordination Centers (RCCs) process the signal and coordinate the rescue effort.

A unique aspect of the PLB signal, compared to other technologies, is that registration is required, at no cost to the consumer. Once a PLB is registered, a code is assigned and transmitted by your unit, which assists in the identification and confirmation of your emergency. Once a signal is received, rescue officials will note the coded signal and consult with the registration information. Within minutes a phone call is made to the registrant's home to confirm the legitimacy of the signal and to ascertain any information possible about the subject and location. Failing contact, rescue units are dispatched immediately.

Registration has an additional benefit. You can file a flight or float plan as well as a plan for a backpacking or hunting trip 24 hours in advance of a trip, and have your intended location entered into a database that is used to assist rescue efforts. Registration and trip plans can be filed at http://www.beaconregistration.noaa.gov.

Depending on your location, you may be rescued by a variety of agencies, military, volunteers or a combination of several. Typically, the U.S. Coast Guard responds to marine distress signals; however, local or state assets that are closer to your location may assist them. The Civil Air Patrol usually responds to aviation distress signals, primarily due to their air search capabilities. Rescues for inland emergencies are usually the responsibility of local law enforcement agencies, which are often assisted by volunteer search teams in remote locations.

Prior to the authorized use of PLBs on land, the primary application for these high-tech survival tools was limited to maritime applications, which the system was originally created to serve.

NOAA satellites helped save 272 people from potentially life-jeopardizing emergencies throughout the United States and its surrounding waters in 2006, up from 222 the previous year. This is the highest number of rescues since 1999, when 294 people were rescued.

Since its creation in 1982, COSPAS-SARSAT has been credited with more than 20,300 rescues worldwide, and 5,396 within the United States and its surrounding waters. Most of the rescues each year happen at sea. The top states with the most rescues in 2006 were: Alaska, with 75 rescues in 29 events (including two dogs); Florida, with 50 rescues in 18 events (including two dogs); Hawaii, with 16 rescues in five events, and Texas had 11 rescues in six events. Since the Personal Locator Beacon program became operational nationwide in July 2003, there have been 125 rescues credited to the hand-held devices.

Within a five-day stretch in November, 18 people and one dog were rescued in nine separate maneuvers from Florida to Alaska. From November 3 - 7, three crewmen were rescued from a boat caught in rough surf near Kodiak, Alaska, and in Barrow, another person was rescued after being stranded.

Meanwhile, two boaters were pulled to safety off the coast of Cape Cod, Mass.; one crewman was saved from a troubled vessel more than 1,000 miles east of Long Island, N.Y.; another two boaters were rescued off the coast of Hilton Head Island, S.C.; two people were rescued from a sinking boat near Ponce Inlet, N.C.; two passengers were picked up from the site of a plane crash near Tulsa, Okla.; one person was saved from a capsized boat 1,200 miles northeast of Bermuda, and four people and a dog were rescued from a sinking boat near Tampa.

COSPAS-SARSAT is an acronym for an international satellite-based humanitarian search and rescue system that reaches all corners of the globe. SARSAT stands for Search and Rescue Satellite Aided Tracking and SOCPAS is an acronym representing the Russian words "Cosmicheskaya Sistyema Poiska Avariynich Sudov", which translates to Space System for the Search of Vessels in Distress," which harkens back to the maritime origins of this international distress alerting system.

The U.S. Air Force Rescue Coordination Center recently conducted a study comparing PLBs to cell phones in attempts to communicate from wilderness areas throughout the United States. PLBs held a definite advantage over cell phones in many circumstances and in approximately 34% of these tests, phones were unable to make contact in areas where there supposedly was cell phone coverage indicated by the phone company maps; and these areas were not even particularly remote. In addition, the attempts were not made in difficult terrain, such as canyons or valleys. The test areas were actually open and elevated; optimized for cell phone performance.

Another important issue for those who put their security and comfort in a cell phone; even if you are able to make a connection, how will you direct your rescuers to your location? Telling your would-be rescuers that you're laying at the bottom of a steep hill, next to a tall tree, won't help much. If you had the foresight to carry a GPS unit, and are able to make a connection, you will be the exception.

A PLB can be used anywhere on the globe; however, PLB activation is prohibited anywhere that radio transmissions are prohibited, such as commercial airlines in flight, in explosive storage or blasting areas.

GPS capable PLBs solve a lot of problems in one small package, by connecting to satellites and transmitting exact GPS coordinates, with Doppler shift analysis to geostationary satellites. Doppler shift calculations adjust for the shift caused by the motion of the satellite compared to the stationary beacon. PLBs designed specifically with internal GPS capability or the ability to integrate external GPS units, such as the ACR Terrafix 406 PLB, are considered self-locating due to the encoded longitude and latitude that are included in the signal.

If you already own a GPS and are considering adding a PLB to your emergency equipment, make sure that your GPS provides NMEA 0183 output. Most modern GPS units comply with this standard, but it is a good idea to check first.

The high-capacity battery used by the Terrafix 406 provides a minimum of 24-hour signal transmission, and even longer in warm weather, which should be more than ample time for you to be located and rescued under most conditions. While PLB units are extremely sturdy and reliable, they can fail, or become damaged in a fall if not protected properly. It's a good idea to carry a loud whistle, signal mirror, and a flashlight or laser beam for night location. When it's your life that hangs in the balance, wouldn't you want to be totally prepared?