The essential point: Rescuers are locating the beacon’s transmissions—not directly tracking the person. Once activated, keep the beacon operating and remain with it unless staying creates an immediate danger.
PLB, ELT and EPIRB: three settings, one alerting system
Modern Personal Locator Beacons, Emergency Locator Transmitters and Emergency Position-Indicating Radio Beacons serve different users but rely on the international 406 MHz Cospas-Sarsat system.
| Beacon | Primary setting | Typical association |
|---|---|---|
| PLB | Personal and remote travel | A registered person |
| ELT | Aviation | An aircraft |
| EPIRB | Maritime | A vessel |
Activation methods, carriage requirements, approvals and optional locating features vary by beacon type, model and jurisdiction. Owners should follow the manufacturer’s instructions and applicable regulations.
The beacon transmits a coded 406 MHz message
When activated, a modern distress beacon transmits a digitally coded signal in the 406.0–406.1 MHz band. The message includes a unique beacon identification code. Beacons equipped to obtain a navigation position may also include that position in the message. A beacon without an encoded position can still be located through Cospas-Sarsat processing.
Cospas-Sarsat detects and routes the alert
Search-and-rescue instruments aboard satellites receive the beacon transmission. Ground facilities process the data, and a Mission Control Center distributes the resulting alert to the Rescue Coordination Center or other authority responsible for the area.
In the United States, NOAA operates the U.S. Mission Control Center with participation from the U.S. Air Force, U.S. Coast Guard and NASA.
Registration helps authorities evaluate the alert
Registration connects the beacon’s unique identification code with owner, emergency-contact and relevant aircraft, vessel or trip information. Authorities can use this information to evaluate the alert, contact responsible parties, identify accidental activations and plan the response. Registration should be kept current.
The responsible authority coordinates the response
The response depends on beacon type, location and jurisdiction. The Air Force Rescue Coordination Center coordinates federal on-land search-and-rescue activity in the 48 contiguous states. That jurisdiction does not include Hawaii or Alaska.
The U.S. Coast Guard operates rescue coordination centers for its geographic areas of responsibility. In Hawaii and the surrounding Pacific region, coordination is handled through Joint Rescue Coordination Center Honolulu under the authority of the Coast Guard’s Oceania District. State, local, territorial, tribal, federal and volunteer organizations may perform or support the field response.
The reported position becomes the starting point
The responsible authority supplies the responding organization with available alert and location information. The position may come from information encoded by the beacon, Cospas-Sarsat location processing or a combination of available data.
Responders may enter the coordinates into agency-selected mapping software for planning, navigation and coordination. Mapping software is separate from the beacon and field direction-finding equipment. Terrain, GPS reception, message content, beacon movement and antenna placement can all affect the relationship between the reported position and the beacon’s physical location.
121.5 MHz supports final homing
Modern 406 MHz distress beacons generally also transmit a lower-power signal on 121.5 MHz for close-range homing. The 406 MHz message supports alerting and identification; the 121.5 MHz signal gives equipped aircraft and field teams a live signal to follow during the final approach.
Once activated, remain with the beacon
A 406 MHz beacon does not transmit one continuous satellite signal. It sends a brief digital burst on a randomized cycle centered on approximately 50 seconds—roughly once a minute. Repeated bursts give the satellite system additional opportunities to receive and process the distress message.
After activation, follow the manufacturer’s deployment instructions. Keep the beacon operating, orient its antenna as directed and give it the clearest practical view of the sky. Do not cover the beacon or antenna.
Unless remaining in place creates an immediate danger, stay with the activated beacon. The alerting system and responding direction-finding teams are locating the beacon’s transmissions. Separating from the beacon can delay final location. If safety requires movement, take the activated beacon and keep it properly oriented and unobstructed as conditions allow.
Do not switch off a beacon during a genuine emergency merely because help has not yet arrived. Leave it operating until rescued or instructed otherwise by the responsible rescue authority.
If activation was accidental
An accidental activation should not be ignored. Contact the appropriate rescue authority promptly and report the false alert because an alert may already have been received and a response may already be underway. Follow the authority’s instructions concerning the beacon.
Read how ground teams locate the transmitting beacon, then compare current field tool categories.