Quick and easy testing of protective contact sockets for correct connection. Wiring errors such as missing PE, N, and L conductors, as well as the swapping of L and PE conductors, are clearly indicated by three LEDs. The active PE test with a touch electrode and LC display warns of the presence of a dangerous touch voltage over 50 V at the protective conductor connection (PE). A test button triggers the 30 mA RCD circuit breaker. Clear indication via LEDs and LC display. An easy-to-understand status table informs about the correct connection (OK, green) and the type of error present (red) in the protective contact socket. Measurement category CAT III 300 V. Additional technical features: Display: LCD/LEDs.