[Digital (406 MHz) Beacons] LEOSAR uses same technique as for analog beacons, but, since beacons are uniquely identified as beacons and have improved frequency stability, response can occur based on first-pass information[28] Doppler-only accuracy is within 5 km (3 mi) – that is, the position is sufficiently accurate for SAR purposes even after only one pass. What's more, the "A-position" (the most likely of the two 'mirror' positions) can be determined valid with 98.5% accuracy after only one satellite pass. This accuracy can be increased to 99.3% using so-called "combined Leo-Geo processing,"[29] and this technique also enables accurate positions to be generated with as little as two or three bursts from the beacon (i.e. less than 4 minutes of transmission) and thus greatly increases the chances of being found even if the beacon is ultimately consumed by fire or is otherwise destroyed GPS Position can be encoded into the Hex Code and can be updated real-time via GEOSAR Encoded GPS position accuracy is about 15 m (49 ft), however, the space in the hex message protocol for position information is limited, so transmitted accuracy is approximately +/- 125 metres Increases in accuracy are a significant improvement over analog beacons – from two possible positions within a 20 km (12 mi) radius, to 15m accuracy at one position; an improvement in accuracy of over 2500. The improvements in accuracy are largely responsible for the advent of the phrase "taking the 'search' out of Search and Rescue" LEOSAR Doppler triangulation is less affected by beacon movement due to improved frequency stability In the future, near-instantaneous detection & position triangulation via MEOSAR [Analog (121.5 MHz) Beacons] 
No detection by search and rescue satellites (coverage ended February 2009) If a 121.5 MHz beacon signal is detected by a ground station or by an aircraft within range, the signal can be located through the use of specialized radio direction-finding equipment dispatched to the area, or by a trained operator using a radio receiver tuned to 121.5 MHz (VHF/AM aeronautical band).