Dear all, I’d like to ask your help concerning some doubts about electromagnetic waves, Faraday’s cage, and so on. I read recently that an instrument with a transmitter that emits a low frequency electromagnetic field (around 15 to 22 Hz) located inside a metal pipeline could communicate with another one located outside the metal pipeline. It seems that electromagnetic field with that range of low frequency could pass through metal (steel) pipelines… Unfortunately the text didn’t give any information about how does it work…So, it drives me confusing because I think about the Faraday’s cage and it couldn’t work… I don’t know how to explain that. How could the electromagnetic field pass through metal pipeline even for low frequency? Could someone please help me? Thank you very much!