Ultimate sensitivity: detects medium sized pistol from 9" distance; large knife from 6"; razor blades and box cutters from 3" distance; foil-wrapped drugs and tiny jewelry from 1". -self-calibrating: digital microprocessor technology eliminates the need for periodic sensitivity adjustments. -rugged, high-impact abs case with reinforced coil compartment. exceeds mil-std-810f (drop test) method 516.5, procedures ii and iv. -large 8" scan surface for quick, thorough scanning. -no tools required to change standard 9v battery (included). -optional rechargeable battery kit available. -sharp audible alarm and bright red led indicates the detection of metal. -momentary push button helps temporarily eliminate detection of nearby ambient metal such as rebar, metal walls. -three-color led indication: green led indicates on; amber led indicates low battery: red led indicates alarm. -operating temperatures: -35° f (-37° c) to 158° f (70° c)