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"thing" on cables


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Posted

hi

 

I know its a bit of a random question, but does anyone know what the point of the plastic things near the end of lots of cables is?

 

they seem to be on most computer cables, figure of 8 power leads, some IEC cables, everywhere really.

 

this is the end of one such cable

 

http://i8.photobucket.com/albums/a22/timmiddleton/IMAG0003.jpg

 

tim

Posted

It's a ferrite core which cuts interference from the cable. I'll come back with the 'official' definition when I find the bit of paper with it on.

 

Edit: Found it online instead.

 

What causes RFI?  Strong signals from nearby amateur radio, CB, FM and other transmitters are picked up by long wires running through the house:  electric power wiring, telephone cables. alarm system wires, etc.  They feed the signals into the TV, the telephone, and the stereo. Long leads to the stereo speakers do the same.  Electronics in these appliances are upset by the RF and you hear the radio transmitter in your telephone and TV and the alarm goes off.

 

 

How to cure RFI - Run the wires through ferrite cores right next to the affected appliance (the Tip Sheet gives details). Ferrites do not affect the signals going through the wires but they resist the passage of RF. So they keep the RF out of the appliance and stop the RFI.

 

from a supplier of ferrite cores. :)

Posted
There's a magnet in there, believe it or not. I was always lead to believe it was to reduce interference or somesuch nonsense. Not sure it actually does and I've never ever seen it on pro kit.
Posted
yeh thats why I didnt think it served any useful purpose. surely if its that good then every cable would have one!

If your professional gear is sensitive to RF interference, it probably should have a ferrite bead on every cable. The reason you don't see them on professional level gear is that the gear has been designed with good RF rejection built in. You see the ferrite beads more on computers or consumer electronics that have not been designed with good RF rejection.

 

Mac

Guest mattladkinlx
Posted
If you notice now even some consumer products now are built to a good enough standard that they are not needed!

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