Non-Contact Voltage Detector- Insulated voltage detector housing ensures safety. Testing can be performed without physical contact and isolated operation ensures safe testing. Portable Pen-Shaped Design- Yolistar's Voltage Detector Pen is designed in a pen shape with a pen clip. It easily clips to your pocket and many other places, allowing you to keep it handy during repairs, making your job easier. Adjustable Sensitivity - Sensitivity is adjustable for more sensitive and flexible measures. Press the S button for 3 levels of sensitivity adjustment. One beep indicates low sensitivity, two beeps indicates medium sensitivity, and three beeps indicates high sensitivity, allowing you to adjust the sensitivity to suit your needs. It meets many needs in residential, commercial and industrial environments. Audible Alarm and Security Lighting - Distinguish what is live from what is not by different frequencies of dimmer sounds. 'alarm. The higher the voltage, the higher the frequency of the audible alarm and the frequency of the LED flashing. The white LED flashlight helps illuminate the work area in the dark.