Patented Ion-Pump sensor with built-in selective filter housing. 0.25oz/yr (7g/yr) leak rate of HFC.. Over 100 computer generated tones varying in intensity with leak size. 10 high intensity bar graph display. Lock-out mode. MADEINUSA The LS790B Leak-Seeker combines the most advanced microcomputer circuitry with field proven Ion-pump sensor technology creating a highly sensitive, accurate electronic refrigerant leak detector. Over 100 computer generated tones and a high intensity bar graph display quickly alerts the user to carrying halogen concentrations. Patented automatic calibration design eliminates the need for manual balance or tick rate adjustments while the user selectable 10 sensitivity ranges enables the LS790B to detect all refrigerants. Lock out mode is a unique feature that enables quick and easy locating of refrigerant leaks in highly contaminated search zones. In this mode, the unit will automatically and systematically store the recorded concentration levels of background refrigerant while initiating leak search, alarming only in the area of highest recorded concentration level, the actual leak source. Operating temp: 0 to 140F / -18 to 60C. 40 hours battery life using 4 "AA" alkaline batteries. Auto OFF after 15 minutes of inactivity.