Good afternoon. A device for non-contact determination of the presence of alternating voltage came across Aliexpress two years ago and decided to order it, the price is quite adequate, and judging by the description, it can determine voltage up to 1000 volts without removing the insulation of the conductor, I ordered two, the second son he works as a power engineer. I received it and tested it at home, I was satisfied with the effect, although it does not always find hidden wiring in the walls, but this is not its purpose. Then he acquired a small equipment maintenance business in another city, and here the tester became simply a necessary thing, because when starting the repair of any equipment, you need to make sure that there is no voltage. My electrician with fifty years of experience at first did not really trust the Chinese device and, in the old fashioned way, checked with an indicator, which needed an uninsulated end of the wire, but gradually became convinced that that it is enough to bring the device to the cable or wire and the result is immediately visible. This tester is similar to a large fountain pen and is convenient to carry in a breast pocket. Its length is 15 centimeters and the cross section is 2.0 by 1.5 centimeters. The principle of operation is quite simple - it is enough to bring the spout (white part) to the live conductor, as an audible alarm sounds, it starts flashing red. Also, the tester has a built-in LED light, which is turned on with a white button, the light is certainly not very good, but it is quite enough to highlight something in the shield. The device is powered by two AAA batteries (little fingers), which last a very long time, I changed it a couple of times in two years. Summing up, I want to note that a non-contact voltage tester is a very useful device. I wrote out two more for an electrician and a locksmith; now, before repair, it is enough to touch the power cable to make sure that there is and is no voltage. By the way, the search for an open circuit is greatly simplified, now you don’t have to climb into the pads at the ends of the wire with an indicator. In general, this tester is very useful for me.