Strange device on A/V cables

[Tom41]

You've probably all seen the cables that convert a 'headphone' jack to two phono plugs.

I've seen a strange, cylindrical object on many of these cables, particularly the ones that come with digital cameras for audio/composite output to TV. It's usually positioned nearer the 'headphone' jack, not the phono plugs.
Does anyone know what it is, and what it's used for?

I vaguely remember taking one of these things off an old broken cable and hacking it apart to see what was inside. It just seemed to be made of solid metal underneath the plastic; no electronics at all.

I would assume it's some kind of filter, but I haven't been able to find any information about these things on the Internet..

[jpdoe]

Re: Strange device on A/V cables

Here you go:

http://www.ce-mag.com/archive/02/11/may.html

[Toasty]

Re: Strange device on A/V cables

It's a choke to filter spurious harmonics and interference from the signal generated by the input device. Usually made of either ferrite or iron powder.

[Wizard]

Re: Strange device on A/V cables

Yes, this is ferrite bead filter (choke). This doesn't let getting past anything that has EMI.

Cheers, Wizard