Features:Self-test function: When self-testing before use, please hold the tip of the pen with one hand and touch the end of the pen with the other hand. The light on indicates that the test pen is normal and the battery is sufficient. No light indicates the battery needs to be replaced.Automatic induction: close to the wire, when the light is on, it means the line is live. The brighter the light, the higher the voltage on the circuit under test.Find the breakpoint of the line: touch the bottom of the pen with one hand, and touch the wire with the tip of the pen. A breakpoint is where the light goes off. It is used to find breakpoints in daily household appliances such as computers, and power strips.DC detection: Please touch the bottom of the pen with one hand, touch the positive pole of the battery with the tip of the pen, and touch the negative pole of the battery with the other hand. When the light is on, the battery is fully charged.Strong Light Waterproof: The pen is designed with a bright LED light, which is also an obviously reminder when using it during the day. What39;s more, it39;s waterproof, allowing you to work outdoors.Reminder: Your hand needs to touch the bottom of the pen, which is the position of the screw rod, otherwise it is impossible to judging whether the line is live or not. Notice:1.Actual color may be slightly different from the image due to different light effect2.Please allow 1-3cm deviation due to manual measurement Description:Product length: about 14.3cmMaterial: PSStyle Description:One light is on for one light: the neutral-line is off, and the red light is on for the live line.Double lights on the traffic light: the line lights up the green-light, and the hot line lights up the traffic lightPackage List:1 x Responsive Electrical Tester Pen