ELECTRICAL WIRING DETECTOR: AC lines are detected in all configurations of the . This configuration provides the best results with detection depths down to 5.1 cm. Wires may not be detected behind concrete walls, plywood partitions, or metal panels. METAL AND FRAMING DETECTOR SCANNER: Suitable for finding suitable places to drill holes, for example when installing drywall. Wood/metal detection depth is up to 3.8/6.0 cm. THREE-COLOR BACKLIGHT: The red backlight indicates when an object has been detected and an audible alarm sounds at the same time. Orange when approaching an object and green when no object is found. NOTES:Wall moisture affects test results. The device is not suitable for detecting concrete walls. We are always available for more specific questions.