What Are These "things" On My Scanner's Usb Cable?

[wpcoe]

I've been curious about this for the several years that I had my previous Canon scanner. Now, I just bought a new Canon scanner with an updated version of the same cable, so thought I would ask the experts (and anybody else who wants to chime in <g>)

On the USB cable that came with each scanner there is a small canister-like thing near each end. The older cable had a clear casing on the canisters and it looked like bits of charcoal in there. As several years have passed, there is now moisture in there as well. The USB cables with the new scanner have a black casing, so can't see inside. I wonder if it were some sort of device to filter out static or electrical interference, maybe?

Here's a photo of the old cable:

[monty]

RF filters!

Ever hear the buzzing noise through cheap PC speakers just before your GSM is about to ring?

It's radio signals from your telephone picked up through the cheap unshielded cable between the PC and the speakers.

Many USB cables have those filters, to avoid data transmission errors when such radio interference is around...

[Tywais]

RF filters!

Yep, more specifically, ferrite cores.

[wpcoe]

Thanks! I knew you guys would know what they were.

Does the fact that the old one now has condensation in the cannister render it ineffective?

[Tywais]

Thanks! I knew you guys would know what they were.

Does the fact that the old one now has condensation in the cannister render it ineffective?

No. The ferrite core and the cable are separate and will not be a problem (such as shorting, etc.). The core is over the insulation of the cable. You will see these on video (VGA/DVI) cables also.