SAFETY FIRST: It will send out multiple alarms through sound and light. When the voltage is detected, the tip will send out red light and beep. When the higher the sensed voltage is, or the closer it is to the voltage source, it beeps at a higher frequency. At the same time, the screen will be red or green, red means high voltage and live wire are detected, green means low voltage and null wire are detected.^ NON-CONTACT: With NCV inductive probe for AC voltage; Just place the tip near a terminal strip, outlet, or supply cord. When the tip glows red and the pen beeps, you know there's voltage present. The live wire detector can automatically detect the live or neutral wire. Ideal for breakpoint Test. Handy circuit tester for electricians, homeowners.^ DUAL RANGE: Detects standard and low voltage (12-1000V AC / 48-1000V AC) for more sensitive and flexible measurements. Press the S button to adjust sensitivity and adapt low range for doorbells, thermostats, irrigation wiring etc.; The NCV sensor automatically recognizes the voltage and displays it on the bar graph.^ SECURITY LEVEL: The electrical tester is safely double insulated. High Voltage Alert to warn you of voltage above 90V, the screen turn red and the safety symbol on the screen shines.^ COMPACT DESIGN: Bright LED flashlight for work in dim ares; Low-Power-Indicator when battery voltage is below 2.5V; Automatic Power Off after 3 minutes without operation or signal detection; Pocket-sized, pen hook allows you to carry it in your shirt pocket.Please feel free to contact us if you have any concerns.