The SOS F1-ND now has seven volume ranges instead of five, giving it the best audio signal of any analog beacon on the market. Changes in volume make it simple to determine how accurately you are aligned with the flux line and help you sense your proximity to a buried victim. SOS has also increased the number of magnitude LEDs from three to seven, which gives a clearer visual signal when searching. The FI-NDs LEDs begin indicating a signal long before any other beacon gives any visual clues. This gives the FI-ND a greater “usable” range than other beacons when audio signals are very weak. The combination of superior audio and visual signals make staying lined up with the flux line easier than with any other analog beacon. Effective range is 90 meters. Other features include: 2 point body harness, built-in battery check, speaker, headphone jack, comfortable contoured body. The F1-ND operates on the 457 kHz frequency and is compatible with dual frequency units, but is NOT compatible with old 2.275 kHz frequency units.