Patented in 18 countries, the hand-held, DKL LifeGuard& detects and tracks living humans by detecting the unique, ultra-low frequency, electrical field created by a beating human heart. Used by the Japanese Federal Police, Hong Kong Fire Service, Taiwanese Search and Rescue teams and others, LifeGuard& can locate standing adult targets in the open air from 500 meters, at shorter ranges through barriers, in almost any weather. A patented, polarized filter makes the passive LifeGuard& human specific. SilentGuard&, an autonomous version of the same sensor, works at much shorter ranges, and may be concealed underground or behind walls.