The detector picks up a beam when it crosses the electronic sensor window. It features three buttons: On/Off, Sound, and Sensitivity. The sensitivity setting allows for either a narrow or broader detection range. When the detector is too high, a slow beep is emitted; when too low, a fast beep is emitted; when aligned with the beam, a continuous pitch sound indicates proper alignment. For accurate results, use the spirit bubble to keep the detector level. Color: Yellow. Material: Plastic. Style: Red light. The detector is powered by a standard 9V battery. Note: This product is compatible only with Rotary Laser Levels. Package Contents: 1 x Laser Level. Only the items listed are included; other products are not included. Note: Light reflection and different display settings may cause slight color variations between the item and the image. Measurement error allowance is +/- 1-3 cm.