An avalanche beacon, also called a transceiver, is a communication device that uses radio signals to communicate with other beacons. All avalanche beacons produced after 1996 operate on the same internationally recognized frequency, 457 KHz, so there's not an issue between incompatible devices unless you have an outdated one.
Beacons include "transmit" and "receive" functions. They emit an electromagnetic radio signal every few seconds when on transmit. The signal is sent in what is called a flux line, which is a curved pattern on both sides of the unit. When set to receive, a beacon is able to receive the transmission from other beacons via an antenna, which results in a beeping sound. The closer you get to a transmitting unit traveling on the flux line, the louder a unit set to receive will beep.
Beacons are a tool that you hope you'll never have to use in a real-life scenario. They have the narrow purpose of finding an avalanche victim after he's buried. It is usually impossible for a person to dig out after being buried in an avalanche, so the only hope of being rescued before running out of oxygen is to be found by others in your party and dug out. According to the U.S. Forest Service National Avalanche Center, an avalanche victim's best chances for survival are if he's rescued within the first 15 minutes.
Digital vs. Analog
Analog beacons are the more traditional style. They rely on one antenna and a simple audible beep system. Digital beacons use multiple antennas and a microprocessor to process the signal into both an audible and a visual display that includes the direction and distance to travel along the flux line. Digital beacons provide more accuracy and are better able to zero in on a victim, while analog beacons have a greater range. Digital beacons are a good choice for beginners but are not necessarily more effective overall. Both digital and analog models use the same 457 KHz frequency and are compatible.
Beacons are the first tool for rescuers to use after an avalanche, but they are part of a system. The beacon provides rescuers with a general location but says nothing to pinpoint where the victim is under the snow. Once a general location is established, rescuers use a probe to penetrate through the snow and find the victim. They are then able to shovel more quickly and effectively. Everyone entering the backcountry should carry a beacon, probe and shovel.
Beacons are only useful if everyone in your party is wearing one. They need to be set on transmit prior to entering the backcountry since you won't be able to switch it one when you're buried. They should also be worn under a jacket and close to the body to help keep the batteries from freezing.
Before entering the backcountry, you should practice using your beacon and get familiar with the techniques of using one for finding a victim. The time to learn is not when your buddy is buried. You should also be certain that others in your party know how to use their beacons; your life could be in their hands.
Even with the trained use of a beacon, it's still possible for a victim to die from suffocation or trauma to the head and body during a fall. The U.S. Forest Service National Avalanche Center cites that one-third of avalanche victims are killed by trauma. As important as it is to carry and use a beacon, it's more important to understand avalanche science and avoid high-risk situations.