Siemens makes DSL stuff, so my GUESS is that the rack of stuff feeds DSL interwebs to people.
And
this says, "To avoid moisture to alter their characteristics, power and telecommunication cables are pressurized with dry air or nitrogen. Leaks will obviously cause a pressure decrease and will make the existing protection uneffective."
Weird, I've never heard of that before. Those telco boxes are more mysterious than I ever thought!