A non-contact voltage (NCV) tester is the safest way to make sure the AC power is off without touching any live conducting parts of wires or switchboards.The NCV tester will light up and/or make noise when it comes close to a live AC current within a wire, switch, contactor, breaker, etc; even if the current is covered by insulation or just below insulating material.The tester flashes red and beeps when it detects an AC voltage over the testers specified voltage detection level. The commonly recommended method of detecting AC power using a NCV is to follow these steps:Step 1. Identify a known live AC power source. Test this known live power source to confirm the NCV is funtioning correctly.Step 2. Test the wire/circuit/etc in question to see if it is live by the NCV flashing and beeping.Step 3. Test the known live power asource again to one more proove the NCV was working correctly.Following these steps should give you high confidence in the NCV result of the in question item being tested.Do not perform test with the hand beyond the hand safety protection and do not allow insulated wires beyond the CAT IV reference mark on the tester.