Measure AccuratelyThis voltage tester can detect voltages: 12V-1000V, and distinguishes them into 3 voltage classes. The BEEP will alert low, medium or high sensitivity with different frequency and LED color difference. Sound & Light BuzzerThe intensity of electrical tester voltage is displayed on the screen during test. If the red LED flashes with alarm in rapid rhythm indicates that the firewire is detected. If the red LED does not flash, it means the zero line is detected. SafetyNon-contact testing and insulated pen body ensures safety. It flashes and beeps when the device is near AC voltage. Voltage can be safely detected without the help of an electrician or professional. Non-Contact Voltage Tester Insulated voltage detector housing ensures safety. It flashes and beeps when voltage tester pen is close to AC voltage. Voltage can be safely detected without the help of an electrician or professional.