Wiring on RJ45 wall socket

I am wiring up some RJ45 network sockets for the first time. (MK Electric part K5845 - available in UK)

If the pins in the front of the socket are numbered 1-8 left to right, then the corresponding connections on the IDC block on the rear are arranged as follows:

4 X X 5

6 X X 3

8 X X 1

7 X X 2

Why is this arrangement used?

I can see how the wires in the pair to terminals 7 and 8 are kept together, as are the pair to 1 and 2.

But you have to untwist the pair going to terminals 6 and 3, as the wires in this pair are on opposite sides of the block. You also have to untwist the pair going to 4 and 5.

If keeping the twist right up to the terminal block is important, why isn't the IDC block arrangement as follows:

4 X X 6

5 X X 3

8 X X 1

7 X X 2

or am I missing something?

Reply to
Pandora
Loading thread data ...

On Sun, 08 Jul 2007 03:22:03 -0700, Pandora mused:

No, you're looking at it too closely, just punch the cables down and screw the cover on.

Reply to
Lurch

I don't know if that ascii depiction of the IDC block is coming out correctly but the distance between the two columns of four is 15mm, whereas the distance between pins in each column (e.g. between pins 7 and 8) is 4mm.

Reply to
Pandora

This might help:

formatting link
Note that there are two standards for connection (568A and568B). It doesn't matter which you use, as long as they are the same at both ends!

The arrangement of the wires and pins is all to do with minimising crosstalk between the wires in the cable.

David

Reply to
DavidM

Thanks

I understand about two standards for connection but my question is about the physical laying of the wires, rather than the colour of the sheaths.

I wondered why the manufacturer had laid the IDC connectors out that way and whether I was misunderstanding why two pairs terminated on opposite side of the terminal block.

Reply to
Pandora

...

Because thats the way they did it? Some of Leviton's jacks are that way too. But they seem to change the layout from model to model. Its probably cheaper for them to produce the circuit boards with the wiring like this that matches the way the wires actually are inside the jack itself.

As long as you can punch down reasonably you should pass certification no problem, its not like they're going to produce something that won't.

Other manufacturers do it differently.

Personally, I like the Hubbell XJack layout which does keep the pairs together (and angeled) as far into the connector as they can.

Reply to
Doug McIntyre

Its just simply the way a particular manufacture laid out the printed circuit board connecting the IDC punch downs to the jack pins. Its not a critical or important thing to worry about.

A Hubble brand 568B physical layout looks like this:

Gold pin side Pin 2 Orange/White Pin 8 Brown/White Pin 1 White/Orange Pin 7 White Brown Pin 4 Blue/White Pin 6 Green/White Pin 5 White/Blue Pin 3 White/Green

Here all associated pairs are on the same sides of the jack.

A Leviton brand 568B physical layout looks like this:

Gold pin side Pin 2 Orange/White Pin 7 White Brown Pin 1 White/Orange Pin 8 Brown/White Pin 3 White/Green Pin 6 Green/White Pin 5 White/Blue Pin 4 Blue/White

With the Leviton, the orange and brown pairs terminate on the same sides of the jacks, and the blue and green pairs are split on opposite sides of the jack.

On a side note, an ethernet jack is properly called an 8-pin jack, but us old timers often still incorrectly call it an RJ45 jack.

Reply to
DTC

OK - you got me to go and look at my stock and they are:

6x x5 3x x4 7x x1 8x x2

They aren't MK, so the question arises as to why you are using data devices made by an electrical company? :-) At least it explains why we shouldn't automatically accept an installation done by an electrician :-) Thanks for warning me...

I'd check that the label on your connectors is actually telling you which pins the PCB is connecting to - it wouldn't be the first time I've seen pin numbers on labels and even etched on a PCB being wrong...

You are correct in saying that you shouldn't untwist the wires more than is absolutely necessary and so they should preferably be on adjacent connectors of a punch-down. If a connector doesn't accommodate the "split pair" (3-6) in it's PCB, I'd find a different make, since it is probably a pre-

100Mbps design.

FYI, some of the first twisted-pair Ethernet installations I used were wired by a site tech, who hadn't seen them before> He used the pairs to pins 1-2, 3-4, 5-6 & 7-8. It tested OK with his cable tracer and 'worked' at 10Mbps but failed at

100Mbps... Guess who had the first 100Mbps device? :-)
Reply to
JohnW

Especially if you're not running Ethernet over it.

Owain

Reply to
Owain

... assuming tab down, this is conventional numbering

[bl] [gr]
[br] [or]

This is a nice layout, it minimizes the pair untwist. Punch down as marked above for T-568-B. For T-568-A, swap the orange and green pairs. Colors on evens.

-- Robert

Reply to
Robert Redelmeier

That's the same as the MK Electric brand. I think that the Hubble brand layout is better but there you go. (I use MK because the network sockets match the profile of the power sockets - it's an aesthetic thing.)

OK, now I know that there's no problem, I'll just wire up as everybody has suggested.

Thanks, guys.

Reply to
Pandora

If it is appropriately Cat5 or Cat6 certified then there is no reason to worry about the arrangement. I would say it is a little easier to design for high frequencies if the two for a pair were closer, but it isn't that hard either way.

Most that I remember have the wires of the pair opposite each other (like (4,5) and (6,3) in your example) for all pairs. It might be a little easier to punch down that way.

-- glen

Reply to
glen herrmannsfeldt

All of what you say is true, Glen, but Leviton, and obviously MK, chose to do it this way. I've used Leviton for several years, and, with the Rapid Jack tool, it's not so bad to fan the wires and seat them all at once. The jacks have a lower profile than most and it fits in a Leviton surface mount housing better than anythng else, so I keep going back to them.

Carl Navarro

Reply to
Carl Navarro

How many jacks did your Rapid Jack Tool do before the cutting blades got dull and started mashing up the jack? Mine has started damaging the jacks after only a hundred or so jacks.

Reply to
DTC

I confess, I only use it for high productivity and that means two jobs so far for about 160 jacks. I am really careful to seat the jack in the slot before I crimp it. I don't get it out for one or two jacks. I have the eversharp 110 blade...and BTW don't drop it on the tile floor bacause Murphy says it will always fall point first. Especially when you're in a hurry.

Carl

Reply to
Carl Navarro

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.