From: Scott Morris (swm@emanon.com)
Date: Mon Jan 03 2005 - 11:19:57 GMT-3
Nothing to do with crosstalk, because anywhere inside the cable, the wires
are inter-twined.
It goes back to old telco history. Cable pinouts for different jacks (RJ
stands for "Registered Jack" in case you care) were set way back when
(before my time). Which particular pins were active became a later
decision, but really has no bearing any anything as interesting as the
crosstalk thing.
The only place those wires are separated is at the actual termination jack.
If you're at a cross-connect, they'll be right next to each other! But the
pairing from the old AT&T USOC (Universal Service Order Code) days has been:
1-2 pair 3
3-6 pair 2 (secondary phone line)
4-5 pair 1 (primary phone line)
7-8 pair 4
EIA/TIA 568A standards are compatible with USOC, and preferred in most
large/government contracts.
Notice that pairs 1 and 2 will really correlate into the RJ-11 (and other)
schemes as well...
Vast collection of useless knowledge. :)
HTH,
Scott Morris, MCSE, CCDP, CCIE4 (R&S/ISP-Dial/Security/Service Provider)
#4713, JNCIP, CCNA-WAN Switching, CCSP, Cable Communications Specialist, IP
Telephony Support Specialist, IP Telephony Design Specialist, CISSP
CCSI #21903
swm@emanon.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Walker, James - Is
Sent: Monday, January 03, 2005 9:12 AM
To: Drew Whitaker; ccielab@groupstudy.com
Subject: RE: Pins 3 & 6 seperated
Just a guess, probably has to do with cross talk.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Drew
Whitaker
Sent: Monday, January 03, 2005 9:01 AM
To: ccielab@groupstudy.com
Subject: OT: Pins 3 & 6 seperated
Had someone ask me today, "Why are the Ethernet UTP receive pins (3&6)
separated while the send pins (1 & 2) are together?" I answered, "Just
because," but I don't think that was sufficient. ;-) Anyone know why it's
pins 3&6 and not pins 3&4?
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