Non-Contact Voltage Detector- Insulated voltage detector housing ensures safety. Testing can be done without physical contact, and isolated operations ensure testing safety. Portable Pen-Shaped Design- The voltage detection pen of is a pen-shaped design with a clip. It can be easily hung in your pocket and many other places, so you can keep it handy during repairs, making your job easier. Adjustable Sensitivity- The sensitivity is adjustable, which makes the measurement more sensitive and flexible. Press the S button for 3 levels of sensitivity adjustment. One beep indicates low sensitivity, two beeps indicate medium sensitivity, and three beeps indicate high sensitivity, allowing you to adjust the sensitivity as desired. It meets many needs in residential, commercial and industrial environments. Sound Alarm and Security Light- Distinguish power on and off by different frequency alarm sound. The higher the voltage, the more often the audible alarm will sound and the LED will flash. The white LED flashlight helps illuminate work areas in the dark. Note - Range: 12-1000V AC 50/60Hz EN61010-1/1000V. The pen requires two AAA batteries to operate, for safe carrying, our pen does not include batteries.