When assembling the electrical system and installing lighting in the apartment, we must check the voltage in the electricity network, among other things, to detect the neutral wire. An electric tester can be used for this purpose. We touch the cord with it and stick our thumb to the head of the screwdriver. If a current flows in the cable, it will be signaled by the indicator lamp, the so-called. neon lamps. The blade of this screwdriver is also used for typical assembly work in an electrical installation.