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 that the center of the detector is properly aligned. 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 Detector. Only the listed item is included; other items are not part of this package. Note: Light reflection and differences in display screens may cause slight variations in the color shown in the image compared to the actual product. Measurement may vary by +/- 1-3 cm.