features: compact, light for carrying and handling. suitable for adult, pediatric and neonatal patient. highlight led display ,easy to read led indicator for low battery bar graph indicates pulse strength rechargeable batteries inside. approximately 20 hours for normal measrement status. specs: spo2 : range 50 % ~100% accuracy 2%(90%-99%) 4%(70%-89%) 6%(50%-69%) method dual wavelength led pulse rate range 30~250bpm accuracy 1bpm battery type 1.2v rechargeable nimh batteries 2000-2300 mah life about 20 hour for normal measurement status alarm low power light alarm environment ambient temperature 5 degree-40 degree relative humidity 85% storage humidity 80% safety class i , type bf