I live in Germany. When I travel by train, sometimes there are cables that run from pole to pole parallel to the train track.
From the lack of insulation between wire and pole, I guess these are telephone landlines, or electrical cables with low voltage.
Sometimes on these black, rubber-covered cables in the summer I see a thick, shiny, metallic or white spiral wound around them for about a metre (3 feet).
It looks something like this sketch:
When it is cold enough for hoar frost to form, the frost on the cables takes on a spiral shape as well. This spiral hoar frost forms not only on the device, but beyond it and along the whole length of the cable.
What is the purpose of those spiral devices on the cables? And why does the hoar frost form spirals?