Wiring help?

[Mike McCarty]

Tim wrote:
> On Tue, 2006-04-04 at 01:31 -0500, Mike McCarty wrote:
> 

[snip]

>>One thing I've wondered: On what basis should one choose between
>>using EIA 568A and EIA 568B? Electrically, they are the same.
>>I've been out of the cable making "business" for several years,
>>so I don't know why there are two standards for this, anyway.
> 
> 
> I wonder if the way some cables are formed makes it easier to wire it
> one way or another?  Hand wrangling the wires into the right place to

The differences between the two standards has nothing to do with
how the wires are connected, it has to do with which colors of
wires go into which holes. Electrically, they are identical.

> crimp on a plug can be a right pain.  You've got untangle wires, cross
> some over others, and get them all to go into the plug the same
> distance.  It would have been a lot easier to do that if they'd come up
> with a wiring arrangement different from the current specs.  i.e. A pair

The reason is that if you plug in an RJ with only 4 pins you still
get connections which can be used for telephony. When ethernet was
first put onto RJ style plugs, it was intended to be compatible
with existing telephony installations. What I wondered about was
the colors of the wires being different. What I didn't know is
that there is a standard for what colors to use for the pairs.
IOW, pair 1 is always orange+white/orange (IIRC).

> on 1 & 2, the next on 3 & 4, the next on 5 & 6, the last on 7 & 8,
> instead of having the break apart pairs and straddle others.  I
> seriously doubt that would have degraded noise rejection.

Doesn't enter into it. The twist does, though.

Mike
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