Locates wood or metal studs up to 1-1/2 in deep. Red LEDs light up every time a stud edge is approached. 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. TruCal technology calibrates to any wall's density and a steady green LED TruCal light alerts the user when the tool is calibrated and ready to scan.