Cat cable query

aliasojo

Before I ask my question, I should point out that I've already networked the house so this is only a 'I wonder why' type of query.

When you connect up all the cat cables to a patch panel for example, you need to keep the twist in each pair right up to the point of connection. I did do this, but I don't know why I needed to do this? What does the twist in the pairs actually achieve?

Bit bored today, hence the random thoughts creeping in.

aliEnRIK

Twisting helps reject EMI

aliasojo

Ah, cheers for the enlightenment. :beer:

bob_man_uk

when you say "twist" do you mean the actual pins in the plug at the end?

because i was under the impression that all cables are twisted all the way through... and that just because they are twisted doesnt mean they are impervious to EMI, you can get various types that are shielded and unshielded

JamesJamz

This is because there are more chances of electrical interference nearer the patch panel then anywhere else (as 9 times out of 10 you'll have the rest of your kit in a cabinet, switch/hub/broadband maybe a server).

If you stop a twist as soon as it comes out of the shielding, one strand could be subject to more interference then another, thus leading to corrupt files, or CSMA/CD collision detection which cannot figure out the correct meaning of the packet....

That said the chances are slim of that happening, but its supposed to be "good practice"

aliasojo

bob_man_uk wrote: »

when you say "twist" do you mean the actual pins in the plug at the end?

because i was under the impression that all cables are twisted all the way through... and that just because they are twisted doesnt mean they are impervious to EMI, you can get various types that are shielded and unshielded

It's the twist in the cables I'm talking about. You need to keep the twist 'as is' right up until the point the cable is punched down. I just never really knew why.

aliEnRIK

Not all cables are twisted at all. Many many are not.
And twisting doesnt reject all EMI, it just lowers it (no shielding completely rejects ALL EMI)