Bosch Truvo Cardboard Digital Locator. The Truvo detector is a simple solution for scanning walls and ceilings to locate metallic objects or live wires. This makes drilling safer when hanging pictures or installing lamps. An LED traffic light system and a warning signal indicate areas where drilling should be avoided. For added convenience, special LEDs with symbols for metal and live wires clearly show what the detector has found. A single on/off button and automatic calibration ensure that scanning tasks can be started immediately. A language-neutral quick start guide with simple graphics helps you use the tool correctly for more accurate results.