Date: Mon, 7 Aug 1995 10:58:39 -0400 (EDT) From: "Don's FList drop" <freelist@elf.kendall.mdcc.edu> To: rhh@ct.picker.com Cc: questions@freefall.cdrom.com Subject: Re: (?) RJ45 Crossover Cable Question (Pin numbering) Message-ID: <Pine.BSF.3.91.950807104321.23782C-100000@elf.kendall.mdcc.edu> In-Reply-To: <9508062304.AA22800@elmer.ct.picker.com>
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You can look in the FAQ for comp.dcom.lans.ethernet, but I bet this has
all the answers you need...
On Sun, 6 Aug 1995, Randall Hopper wrote:
> In short, does someone know the convention for numbering the pins on an
> RJ45 cable connector? If the cable w/ attached connector is held in front of
> you, pins on the near side of the connector and pointing up (cable attached to
> the bottom), are the pins 1-to-8 numbered ascendingly from left-to-right or
> right-to-left?
Liberated from: Linux Ethernet-HOWTO-5.html#ss5.2
5 CABLES, COAX, TWISTED PAIR
5.2 Twisted Pair
If you are only connecting two machines, it is possible to avoid using
a hub, by swapping the Rx and Tx pairs (1-2 and 3-6).
If you hold the RJ-45 connector facing you (as if you were going to
plug it into your mouth) with the lock tab on the top, then the pins
are numbered 1 to 8 from left to right. The pin usage is as follows:
Pin Number Assignment
---------- ----------
1 Output Data (+)
2 Output Data (-)
3 Input Data (+)
4 Reserved for Telephone use
5 Reserved for Telephone use
6 Input Data (-)
7 Reserved for Telephone use
8 Reserved for Telephone use
Some cards, like the wd8013 can sense reversed polarity, and will
adjust accordingly. Also note that 3 and 6 must be a twisted pair. If
you make 3-4 a twisted pair, and 5-6 the other twisted pair, your
cable may work for lengths less than a metre, but will fail miserably
for longer lengths.
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