From company website: "MultiScanner HD900 1 Step multi-function stud finder quickly and easily locates studs and joists behind walls, floors, and ceilings. It also locates metal as well as live AC electrical wiring. A 4-mode switch makes it easy to change functions, while the ultra-bright display screen, SpotLite Pointer, and audio tone all indicate the location of the target. The signal strength indicator helps to distinguish between shallow and deep targets."