On Tue, 2 Mar 2010 08:40:39 -0000, "N_Cook" wrote:

When such a ferrite cylinder is slid over shielded cable of a laptop supply
cable, ie one conductor housed within a sheathing and the ferrite around the
outside of that

Of course they work. No sane manufactory would intentionally design
cables with giant blobs near the ends.

There are multiple flavors of material, composition, size, and shape.
The ferrite clamp on cylinder that I think you're referring to is
usually necesary to prevent the laptop and the switching power supply,
from radiating EMI and RFI. The FCC gets rather irate when that
happens. Everything will work without the ferrite cylinder, but will
not pass Part 15.

http://www.howstuffworks.com/question352.htm


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Jeff Liebermann
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