The SpotLite Pointing System, an audio alert, and a green LED signals when the stud edge is reached. Should scanning begin over the over-the-stud indicator alerts the user to start the scan in a new location. Highlights: Stud scan mode locates edges of wood & metal studs up to 3/4 inch 19 mm deep Ready light indicates when calibration is complete & tool is ready for us Edge arrow lights up sequentially as tool approaches stud & fully illuminates when stud edge is located Zircon s patented over stud feature alerts if scan begins over stud Wire warning detection indicates presence of live, unshielded ac electrical wiring up to 2" 50 mm deep Spotlight pointer shines an arrow shaped image on scanned surface to clearly indicate edge of stud "V" marker groove enables accurate marking of stud edge location Ergonomic grip for secure hold in either hand at any angle Uses 9 volt Battery (Not included)