On 22 Oct 2005 16:27:29 -0700, "dale"
wrote:
So... here's the sp. I've bought a house and all the rooms have Cat 5
cable already in place. The wall sockets are labelled 568B on the
inside and, in order, the wire pairs are BLUE/ORANGE/GREEN/BROWN. All
the cable runs go back to the attic but the previous owner has removed
the patch panel and so all the cables are now unterminated. I believe
that ethernet uses the 2nd and 3rd wire pairs so, for 568B, pins 1,2,3
and 6 should be w/o,o,w/g and g. Pins 4,5,7 and 8 should be
bl,w/bl,w/br and br.
I'm cheap and I don't want to pay for a new patch panel.
What I want to do is simply attach RJ45 plugs to the unterminated ends
and plug them into a cheap switch but... if I wire the plug to either
the 568B or 568A pattern it fails. I know that the switch is sound as
I've tested it working using cables I made up - which also suggests I'm
using the crimps correctly - so what am I doing wrong?
Being cheap, mainly.
For my own installation I've used only Krone or Molex stuff (using
transitions and patch panels and know what I've got.
However, I have seen cheap wrongly manufactured outlets and patch
panels where the connector labelling is simply wrong - being neither
T568-A nor T568-B. Where wiring was done using patch panels and
outlets from the same manufacturer, all was well - it was consistently
wrong.
This is one possiblility.
A second is that the previous owner has wired incorrectly.
Thirdly, when you crimped the connectors did you do them the right way
round? This is a common mistake.
Looking at the RJ-45 with the clip facing away from you, Brown is
always on the right, and pin 1 is on the left.
Again you can get this consistently wrong and a cable with both
connectors wrong, still works.
Fourth possibility is that the one or more of the wires at the outlet
socket is not punched down properly or that there is a break in the
cable. Any of the four wires being broken or shorted will cause the
cable not to work.
To check these latter points, you need to do a continuity and correct
connection test.
You can either do this quickly and quite cheaply by using a simple LAN
tester like Maplin N75CC £12.99, N59BY £19.99, or A35CJ £19.99 or any
one of a number of others.
These work by having one box which puts a DC voltage on each pair in
sequence and has a second box with 4 or 8 LEDs which will flash in
sequence if all is correct; or flash out of order, red rather than
green or with missing or more than one LED in the sequence according
to the problem. You attach one box at one end and the other at the
opposite end and cable problems become quick to find.
You can, of course, make one:
http://www.atomiccomputers.com/projects/cat5t/
but I suspect that by the time you had bought the bits, the component
cost would be not far short of the £12.99 to buy one.
Alternatively, if you can get a helper willing to spend a lot of time
on this, you could run a single wire from your location to where they
are at the other end and have them connect it to each wire in turn
while you use a continuity tester, one wire at a time. That would
give you continuity and position confirmation, but not shorts without
testing every combination.
Having said all of this, since a 24way patch panel can be obtained for
as little as £25, the exercise of titting around making up cables
seems a huge waste of time. You don't have to buy the £100 Krone
ones.
Either way, I think that a LAN tester would save a lot of frustration.
--
..andy
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