Structured Wiring Systems - new wiki article

[Andy Burns]

1 isn't entirely true, some DVI displays you can accept HDCP content.

[Dave Plowman (News)]

My TV has a DVI input and handles the HDMI output from my HD satellite tuner just fine - via an HDMI to DVI lead. No audio, of course. That has to be fed separately.

[dennis]

True, hdmi is dvi + sound on the same connector. I just lump them together.

[dennis]

I forget that some people don't know that hdmi is just dvi on a different connector, sorry.

My TV is the opposite, it has hdmi with one hdmi having an additional pair of audio jacks so you can have dvi with sound connected rather than the digital sound. I just bought a new graphics card with hdmi on it for £30.

[Dave Liquorice]

That is were I may have an advantage my day job involves coiling and uncoiling cables anything from a 3mm dia 1m long jobbie to something

3/4" dia and 50m long. Different cable sizes/types need different techniques. The little one would probably just get the put the "twist in coil" method, the bigger wouldn't be coiled but "figure of eighted". Something in between say 1/4" dia and 30m long would be hand coiled but in such away that the twists cancel out.(*)

The large long bundles show laid out down the lawn in the FAQ I'd figure of eight and tape/tie the loops to keep them as loops and the

8 shape maintained.

(*)I'll try to explain, most people when coiling a cable put a twist into the cable to form the loop hanging down from the holding hand. The trick is to put those twists in in alternate directions. The gotcha is if you take one end through the center of the coil when uncoiling it you may end up with a string of knots. Take a peek at the these vids, I use the first method (all the others seem cack handed to me) but the result is the same.

?v=kLBUzmA4kTU is completely different method:

[RubberBiker]

AIUI it isn't quite as simple as that:

dvi and hdmi are plug compatible, all the capabilities of hdmi, particularly hdcp are not - and may result in blocking or down- conversion of resolution.

[John Rumm]

Similar to how I handle them - I normally make a few coils, and then introduce a reverse twist and then a few coils the other way etc. So you are not twisting it as you go.

With big cable forms its often easier to have someone or something to lay them onto since you can't get that many coils in your hand at a time.

long flex!

[Pete Verdon]

Same with the large lines on sailing ships. Last time I went on Stavros (

) they had stopped teaching trainees to coil in the hand at all, presumably to keep things simple. It's also easier to get consistent sized coils on the deck as well - always 4 planks wide :-)

Pete

[Phil Addison]

Article much appreciated John, especially sections 1-3 that answer the question long in my mind "what thef' is structured cabling all about?". But any idea why its called structured? It doesn't seem to have any structure at all, just a clever method of re-configuring, the price being that you put in loads of wiring much of which may never be used (at least concurrently). I always assumed 'structured' implied some kind of hierarchy. Well, now I know, thank you!

A couple of minor points reading through the rest of it...

How many wires/pairs are there inside a catx cable? Perhaps mention that catx cable is what you are familiar with connecting your computer to router/cable modem (so long as its not a USB cable modem).

In "Material (10).." definition of LAU has not yet been given. It's found much later near the end of the article.

Phil

[Bernard Peek]

In message , Phil Addison writes

There are four pairs in the cable. For 10 and 100Mbit connections only two are used. In theory it's possible to run a second connection over the other two pairs but that's not to be recommended if you can avoid it.

1000Mbit connections use all four pairs.

[John Rumm]

Well there is a hierarchy - however I have only concentrated on the bit of it that is likely to be of interest in a domestic or small commercial setting (the so called "horizontal cabling" where a central hub fans out to individual work locations).

More structure comes in when you start to consider backbone cabling (i.e. cables between central hubs, and hubs / server rooms), "Entrance" cabling - i.e. getting external services like phone and data links into the central hubs etc. You can even consider the patch lead cabling from fixed wall ports to equipment separately if you want (which, thinking about it I ought to mention in the article).

(have a look at he wikipedia article link at the end - that gives a slightly bigger picture)

In Cat5e there are 4 pairs. Of which an analogue voice channel will use

1, a 10 or 100 Mb ethernet connection will use 2, and a gigabit or higher ethernet connection will use all 4.

Ta, I will go fix...

ok, try that; a modified "how does it work" section...

[Phil Addison]

Perhaps worth mentioning that this one is totally passive, whereas more complex ones would (presumeably?) have some computing power at intermediate hubs.

Haha... so big it needed a fish-eye lens to take it. I did spot that at the end they say "Cabling standards demand that all eight connectors in Cat5/5e/6 cable are connected, resisting the temptation to 'double-up' or use one cable for both voice and data."

At end of 1st "How does it work" para, should be "Each of them IS then terminated..."

"joined together"?... Looking at your close up photo, or better still the close-up of close-up :), the RJ45's can be seen grouped in blocks of

6, but surely each socket is connected to a unique cable not paralleled up, or am I missing the point?

Seems to me that each individual 'long' cable in your loom is tetrminated at the push-down connectors on the back of one of the RJ45 sockets visible on the front of your patch panel. These RJ45s are signal 'destinations' typically connected to a wall plate in a distant room.

Other RJ45 sockets could be 'sources' with short lengths of cable connected at the back, typically plugged in to say a nearby router or broadband modem. There are exceptions such as an 'source' phone line which will be a long cable running back to an incoming BT (or other) master socket.

If I'm on the right track then, in your photo the grey cables are phone line 'patch cords' linking your phones to the PABX at the bottom, and the blue ones are short catx 'patch cables' linking the central network switch to various remote computers or other network devices.

All this, or the real answer, must be obvious to those that have done it, but I just spent 1/2 hour googling and nowhere, even

could I find what wiring lies behind the front of a patch panel!

Phil

[John Rumm]

Well the cabling system is passive in most cases. You could perhaps lump the switches / routers / gateways etc in with it. Other than sophistication of the switching gear (larger setups may use "managed" switches rather than dumb ones typical of home use) its much the same.

(some of) the computing power in a corporate environment may be in dedicated server rooms. In a home its more likely to be distributed around in a peer to peer fashion. Having said that its equally likely that you would place some computing resources at the hub location - like network attached storage to act as backup or media streaming storage.

(not sure that helps!)

Sorry not a good choice of wording there. Each socket is independent from the next. They group them slightly to to make keeping track of which socket you are wiring a bit easier.

One does not usually make a patch panel a source (unless using it to say split a phone line into two). Typically the source will be the PABX or Ethernet Switch, or broadband router etc. The proper rack mounting versions of these usually present RJ45/RJ11 sockets to the front to make patching to the panel simpler.

Yup. Some PABX systems may use RJ45 sockets - which means ordinary ethernet patch cables can be used for everything. The one pictured uses RJ11. So I simply bought a number of long RJ11 to RJ11 cables and cut them in three - adding extra connectors to make up some shorter phone patch leads.

Well its a bit dull, but have a look near the end in the wiring up section:

is the group of krone type punch down connections for sub section of six sockets. The terminal positions are colour coded for 568A and B wiring schemes (somewhere on the back it tells you which is which in small print!) (I have used 568B wiring there)

So the wires come into the back of the cabinet, and get terminated one to a socket as shown here.

What other explanations / photos do you think would make it a bit clearer?

[Phil Addison]

Is it worth adding this rider as counter to the bits where people might be tempted to economise and share individual twisted pairs? Especially with gigibit becoming common.

I'm probably reading too much into the term 'patch'. To me it indicates connecting sources to destinations via patch leads, as in the original telephone exchange where someone making a call is connected to the receiver (although in this case the sender and receiver will sometimes be reversed). In your photo all the patch-panel sockets appear to be destinations, the actual patching being done between the 'patch-panel' itself and the other equipment. In effect the 'patch-panel' is only being used as a termination panel. Nothing wrong with that, but could do with clarifying for newbies to the subject, like me :o).

Then they are RJ11 to RJ45 patch leads now?

I can't reconcile that

with this one because the spacing between the RJ45s in the 1st is much less than the punch-down blocks in the 2nd. Why 2 rows in the second pic, or are we seeing the rears of two patch panels? I suppose there must be a catx wire connecting each terminator block on the rear of a patch-panel to its corresponding RJ45 on the front?

Ideally a photo of a patch panel from above showing the complete route through from a patch (or other input) lead at the front to a loom lead at the back, plus the bit above explainning that patching does not have to, or doesn't usually, happen on the patch-panel itself .

Thanks for the additional clarification, of an already excellent article

- its taken me from "what thef' is structured cabling all about?" to "I think I've got it"!!

Phil

[John Weston]

Very good addition, IMO, after having had to sort out some rat's nests.

One omission as far as I can see is the subject of cable labelling. Even on a simple system, it is good practice to label the cables at least at each end. There should also be some labelling of the sockets, behind the removable window. This will make it easier to trace problems or do the initial wiring up to the terminations. Remember it may not be the installer who is doing the maintenance.

Perhaps also include a section showing the various types of cable marker available and some alternative DIY ones, with a warning not to use ordinary tape that will unwrap itself, or Sellotape that goes brown :-) The cheapest I've used for casual installations is a permanent marker pen that can be used to write on the actual cable, but this can be missed, if you forget to put a mark all round the cable...

I wouldn't like to sort out your bundle of cables in a restricted space after you've taped them up, as in the garden picture :-) Not everyone has a cable tracer... (Link required to a suitable model?)

How about a note to include a pull-through if the cables go through an inaccessible void? If this is included, make a note that it should be double length with the pull loop in the middle, so it isn't single use should someone forget to pull through a replacement along with the cable...

How about noting the use of cable trays or similar support for large cable looms? Can be DIY types.

Also add a note about not running structured cabling alongside Mains or similar interference-source cables.

[John Rumm]

In most cases there is no sender or receiver - both PABX and ethernet are fully bidirectional with connection equally likely to be initiated at each end.

Yup I see what you mean, and you are correct in the sense that each socket is like a connection to a "subscriber".

No, RJ11 to RJ11. You can take advantage of the fact that the smaller versions of the RJ45 (more correctly 8P8C (eight pole, eight contact)[1] such as the RJ11, will plug into sockets with more ways and still perform correctly.

You can even plug a RJ10 (4P4C) as found on a telephone handset, into the 6 and 8 way sockets.

[1] >> All this, or the real answer, must be obvious to those that have done

I could do with another photo I think that shows you the patch panel from the top. Yes the second photo is the back of the patch panel.

If you could "look through" from front to back you would see each socket is tracked to a krone strip, and they alternate side to side to make space for the strip of 8 punch down terminals which is wide than the physical 8 way connector:

1 3 5 ###### ###### ######

ok, will see what I can do.

Now all we need do is get to the "where can a buy one" and the job is done!

;-)

[John Rumm]

Good point - you can see it in the photos, but I have not really covered it in the text.

You can probably skip this on a domestic setup since the groups of sockets will be identifiable generally by location. i.e. the sockets on the patch marked "kitchen" end up at the sockets there. The convention that the left socket will always be the lowest number then takes over.

Obviously in an office with 30 sockets, numbering both ends takes on more significance! ;-)

The little dispensers that give a white sticky tab with clear section are quite good. You write on it in the dispenser, adn then pull the label out. As you wrap it round the cable the later clear section acts to protect the written on white section.

Yup will add a link.

On my bundles I wrote the pair number on every other taping (plus each end), before I grouped the pairs into larger bundles. I figured just in case I ever needed to identify which was which mid span.

I might add an example numbering table etc, to re-enforce the message!

Yup, although that might be covered in the electrical installation article that deals more specifically with cable installation techniques.

Could do...

I thought I had mentioned that somewhere... yup - last para of "Design" section.

[Ron Lowe]

Good article.

There are a couple of things I'd be inclined to add:

1) 568B is the most common standard in use for fixed wiring, and I'd suggest using that. The colour-coding on the back of your patch panel there is marked up for both, that is pretty much standard. 2) The way analog telephony is carried over structured cabling could be expanded a bit, it's not always the case that the ring signal is re-generated at the LAU. There are 3 different types of LAU: PABX master, PSTN master, and Secondary. This may be worth a bit of explanation. It may be also be worth linking to this page:

Oh, and I can't let this pass...

An *Analog* pabx?

Get yerself an asterisk box, man!

[Phil Addison]

Indeed; I should have kept to source and destination.

Ahh I see. Does that mean you can't get short RJ11 to RJ11 patch leads? Could you make them up from scratch from a length of phone cable, after all, you must have had to crimp 4 RJ11s per 3 leads, so having 2 on already seems a marginal benefit.

Eeek!

Aha, now I HAVE got it. The missing bit of know-how is that a krone block is the same width as two RJ45 sockets so 2 krones one above the other just fit in the space of the 2 RJ45s they serve. Just out of interest, what do you mean by 'tracked'? Is it on a pcb, a film wire or actual catx cable? Whatever it is still has to meet the catx spec.

The diagram above explains it quite nicely, and feel free to use any of the text of my interpretation.

Err... there's just the little matter of needing to move furniture, lift carpets, floorboards everywhere!! I'll have to stick with wireless, and maybe get some homeplugs, for the time being. But least I know what I'm missing now!

Phil

[John Rumm]

Even that is a bit nebulous...

Oddly enough I have not seen any... I am sure you must be able to buy them. I just used ordinary RJ11 patch leads to start with (i.e. the type you get with a ADSL modem), but that meant you had a clump of extra cable to coil up etc each time. To keep the rats nest under control a bit I ended up shortening them.

Indeed you can. I just went with what I had to hand - however I did not cover it in detail in the article since it was not that important to the concepts.

that quite well - you can see the outline of the RJ45 socket clearly beside the punch down block.

A PCB. Again like in the module in the piccie above. The patch panel just having a long narrow PCB.

I will get another photo at some point. Alas I have not got any more patch panels on my stock shelf, so will either have to wait, or go unscrew one of mine from the cabinet.

;-))