Press the green button to start device， flash twice fast indicates the device has been started and work normally.The user must hold the device， otherwise it will not work normally.Please do not touch the white tip with your fingers when detecting.2 AAA(LR3) batteries， slide the battery cover backward to replace battery.Check the relative voltage on several points (continuous light) through the line (esp. the stripe line)If no voltage checked (no continuous light)， it means the line possibly break.Check ground connection (continuous light means unsafe).Voltbeat TM technology and self-check continually， let your know the device is in a working state.When detecting the voltage， the probe will light and send buzzing sound.Conform CAT IV 1000V safety protection grade， enhance protective performanceFeatures:Sensitivity Range:200-1000V AC (E1/E2/P1)Storage Temperature: -10/50âHumidity: 95% (0-30â)Altitude: 3000mPolluted Grade: 2Size:153*25*18mm， or 6.02*0.98*0.71inNet Weight:31g， or 1.09oz battery not includedPackage Includes:1 x Voltage Detector Pen