What is a PLB?
A Personal Locator Beacon (PLB) is a small, battery-powered emergency transmitter carried by individuals — hikers, climbers, mountaineers, kayakers, solo sailors — that, when manually activated, transmits a distress alert at 406 MHz to the COSPAS-SARSAT international satellite search and rescue network. Unlike an EPIRB (designed for maritime vessel use with automatic water activation), a PLB must be manually activated and is registered to an individual rather than a vessel.
How it works
On activation, the PLB transmits a 406 MHz digital burst signal every 50 seconds, containing a unique 15-digit identifier (the Beacon Identification Code, or BIC) registered to the owner in a national database. MEOSAR satellites aboard GPS, GLONASS, and Galileo navigation satellites detect the signal within minutes, calculate position using Doppler processing (and GPS data if the PLB has an integrated GNSS receiver), and relay the alert to the appropriate Mission Control Centre. The MCC looks up the registration, contacts the owner's emergency contacts, and dispatches Search and Rescue coordination to the indicated position.
PLB vs. personal SPOT trackers
PLBs operate via the internationally coordinated COSPAS-SARSAT system — free to use after purchase (no subscription), globally operated, and formally coordinated with national SAR authorities. Commercial tracking/messaging devices (Garmin inReach, SPOT) provide two-way messaging and tracking via commercial satellite networks (Iridium, Globalstar) but require ongoing subscription fees. PLBs are preferred by regulatory bodies and professional rescue organisations for reliability in formal SAR operations.