568A and 568B

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 Question by Larry Kutner posted 08 Jul 2005
 568A and 568B
I just had FIOS installed at my home office by Verizon. It's hooked up to some structured wiring (Cat-6/RG6/Fiber) that I've just installed in my house. I'm using home runs to a Honeywell FutureSmart panel.

All of the ethernet runs we did in the house are wired to the 568A standard. Verizon insists that the cable coming from its Optical Network Terminal to my panel be wired to the 568B standard. The system seems to be working well. (It's the first day.)

However, I've been told that we might have crosstalk and EMI problems if we use both standards. (Note that we're not mixing them on a single cable, which I know would lead to problems.)

Is this really a concern? Are there different twists among the various pairs that have different effects on CAT-6 cable?

Thanks you for your help.

--Larry Kutner
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 Answer by Joseph Golan posted 09 Jul 2005
Dear Larry,

Either the T568A or the T568B wiring standards can be used, the only difference between them is a swap of pairs 2 & 3 and as long as both ends are the same, it will be transparent to the equipments (electrons are color blind).

I am waiting on my FIOS upgrade (now on DSL) to see if it really is better.

As most home networks are 100BaseT Ethernet, they use pairs 2 & 3 only only. The installer obviously was just talking through his hat about EMI and crosstalk.

The only time it really comes into play is if your closet end is on blocks instead of patch panels, then the appropriate (matching) adapter cord will be needed for the modular connection.

Yes there are twist differences in a cable comparing the pairs but ALL 4 pairs must meet the standards. Like I said before electrons are color blind. Enjoy the FIOS service.

BTW the T568A wiring standard is the proper one for residential use. You will be fine.

Sincerely,
Joseph Golan, RCDD

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