This Small Business Innovation Research (SBIR) Phase II project will demonstrate a capability for locating imperiled firefighters in buildings using wireless technology based on long wavelength signals that penetrate buildings with lower perturbation than observed at higher frequencies. The system is being developed for firefighters (estimated 5 year market of over $150 million) but is useful for any application requiring geolocation in buildings where GPS cannot work. Such applications include tracking personnel and equipment in crisis situations, military combat, inventory management and police and military training. This concept has significant advantages over competing technologies; ultra-wideband solutions pose frequency licensing problems, and man-portable inertial units are bulky, costly and have significant time-dependent errors. <br/><br/>The Wireless Firefighter Lifeline (WFL) system is completely mobile and supports multiple firefighters. It complies with Part 15 rules and will not require FCC licenses. Phase II will demonstrate the underlying technology over a wide range of conditions and will produce a prototype system that will serve as the baseline for future system development. It provides extensive commercial and societal benefit, offers performance superior to that of other potential technologies, and is well positioned to attract further funding.