This easy-to-use combination measuring device brings professional measurement technology into the home. A unique feature in this price range is its ability to detect not only the mains frequency (50 Hz) but also the biologically significant frequency of railway overhead lines, which can often be detected even kilometers away from the tracks. Additionally, the natural harmonics of the mains electricity, such as those from transformer stations, are reproduced accurately. The high resolution is also unique, allowing for a meaningful comparison even with strict building biology limit values.