Why two universe selection jumpers on the hubs?

[frankr]

I do not see any documentation on why there are two or what they do.  I have been following the development since the beginning but I have never understood this...

If they are set different what does it effect?

Frank

[rrowan]

one jumper per wire for each pair of wires.

clear as mud? 

Rick R.

[chrisatpsu]

your universes come in on wire pairs.
1&2  Universe #1
3&4  Universe #2
5&6  Universe #3
7&8  Universe #4

the jumpers are the "switch" to which universe you want to use.
one of the jumpers selects the odds (example for universe #1, it selects pin 1)
the other one selects the evens (example for universe #1, it selects pin 2)

[frankr]

OK that makes sense. That was bugging me. One jumper for each wire in the pair so you have to select both.

Now I can sleep at night 

Frank

[n1ist]

The pixelnet document has an error; the actual pairs are
1&2
3&6
5&4
7&8
This corresponds to the way the wires are twisted together in the cable (for historical reasons from the way phones are wired).  The twisting helps reduce picking up noise from outside sources or from the other twisted pairs in the cat-5 cable.

But yes, the two jumpers are to select which pair of wires are being used.
/mike

[chrisatpsu]

good point...

(unless You're using a 10baseT {258A} cable, but i wont go into that.)