Garden Antiques For Sale

What are the hanging metal pieces on suspended telephone wires?

I found one picture with a caption saying it is a stabilizer: http://img1.photographersdirect.com/img/14852/wm/pd773224.jpg
But how would this piece of metal shaped like a rooftop act as a stabilizer?
What is the name for this metal piece and where can I find more information about it.

The shape of it changes the resonant frequency of the wire as it moves. I know you have seen the film of the bridge that was torn apart by wind moving the bridge at resonant frequency. The same this applies here. If you just added weight to the line, you would change the resonant frequency, but it would still be constant and it would just change the amount of wind needed. The flap design changes the frequency based on its angle and that angle changes depending on wind speed so that it is impossible for the wind to maintain resonant frequency.

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