PERSONAL LOCATOR beacons (PLBs) have recently become available to American citizens. Although they are expensive, they are powerful and accurate signaling devices. When you purchase a PLB, you are assigned a personal frequency code when it is registered.
Be sure to carry extra batteries and take in on hiking trips such as the Appalachian or Pacific trails. Even routine trips can be an advantage as emergencies are never anticipated.
When you activate the beacon, it sends out two signals. One at 406 MHz goes to a satellite alerting rescuers for your emergency. The second, to 121.5 MHz, attracts searchers on the ground. When coupled with a GPS program, the PLB will lead rescuers to within several dozen yards of you.
Note: Always carry a flashlight and whistle with you. These will help the rescuers find you.
Very important tips about PLBs
Sending out a false signal is punishable by hefty fines. Activate the beacon in a real emergency. Store your PLB in its waterproof container. Register your emergency medical details when you purchase the PLB; it will be available to the rescue team.
Some PLBs are smaller than a brick and weigh slightly more than a pound, adding weight to your backpack. This could be a lifesaver and is worth that weight.
I do always have at least one source of light with me.