Circuit Sensor Technology: Innovation in safety the SKIL rechargeable 4V cordless screwdriver’s unique circuit sensor technology is a patented feature that detects live wires in outlets, switches, cords, and fixtures from up to one inch away. Simply hold the cordless screwdriver near the source of electricity and press the detection button. If the circuit is live, the red light illuminates and an alert sounds. With this feature, you’ll always know where live circuits are located before getting started on your project. Every home needs a go-to power screwdriver like this for small projects. More About This Product: - 230 RPM - Easy to use - Circuit sensor technology - Automatic spindle lock feature - Integrated rechargeable lithium-Ion battery - Micro USB charging - Dual LED light.