Date: Sun, 6 Aug 1995 23:58:43 -0400 (EDT) From: Chuck Robey <chuckr@Glue.umd.edu> To: rhh@ct.picker.com Cc: questions@freefall.cdrom.com Subject: Re: (?) RJ45 Crossover Cable Question (Pin numbering) Message-ID: <Pine.SUN.3.91.950806234730.4306D-100000@mocha.eng.umd.edu> In-Reply-To: <9508062304.AA22800@elmer.ct.picker.com>
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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?
>
> ------------------------------------------------------------------------------
>
> The more detailed version:
>
> I recently purchased an ethernet board for my FreeBSD box and am having
> trouble getting it to talk to my router. I suspect that the cable might be
> the problem.
>
> The cable (custom made by someone else) is supposed to be an RJ45
> crossover cable which I'll use to direct-connect to my home router. I've
> buzzed it out to verify that pins 1-3 and 2-6 are swapped. If the answer to
> the numbering convention question above is right-to-left, they are. However,
> given that it isn't working and my board appears to be working fine except that
> it can't put a packet on the network, I suspect that the the convention is
> in-fact left-to-right, and the person that built the cable cabled it backwards.
> If someone knows which is correct, please drop me some e-mail.
>
> Thanks in advance.
>
> Randall Hopper
> rhh@ct.picker.com
I haven't used this for anything but standard telco data interfaces, but
I do know those. Here's the data from the GTE Network Interface Manual
For Registered Terminal Equipment:
1 -- NC
2 -- NC
3 -- A (a control lead for keysystems)
4 -- R ("ring" lead, conventionally red in color, one of the two voice
communications leads)
5 -- T ("tip" lead, conventionally green, also a voice communications lead)
6 -- A1 (another keysystem control lead, actually ground return for the A
lead.)
7 -- PR (one end of the programming resistor, to set audio levels)
8 -- PC (the other end of the resistor from PR).
The parenthetical comments are mine. The colors on the T and R leads are
a pretty strongly adhered to convention, at least among telco people, so
that can be used to identify leads 4 and 5.
The interface is unfortunately used for voice only (non data modem)
applications in a different way, so I wonder if you can really draw any
strong conclusions. Check the interface wiring for RJ-31X and RJ-41S for
comparison on that. The wiring I show is for the RJ-41S, which was used
for data modem connections. Not really common for that anymore, tho.
----------------------------+-----------------------------------------------
Chuck Robey | Interests include any kind of voice or data
chuckr@eng.umd.edu | communications topic, C programming, and Unix.
9120 Edmonston Ct #302 |
Greenbelt, MD 20770 | I run Journey2 (Freebsd 2.0R) and n3lxx
(301) 220-2114 | (FreeBSD 2.0.5-snap) and am I happy!
----------------------------+-----------------------------------------------
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