ADSL Extensions Wiring (UK)

Due to popular demand (well, necessity... ) here's the ADSL Extensions Guide For The Telephonically Uninitiated.
Seriously though, if you feel this stuff is heavy going, please don't plough in and hope for the best. We don't intend that this be regarded as some kind of Cables For Dummies. If you're an actual Dummy, bite the bullet and pay a professional installer.  Please.

Assumption
You know the old "never assume" motto? How valid, how very valid. Still, sometimes you have to, but at least we're going to tell you our assumptions. This article is written assuming that you're going to be using the NTE5 type Master Linebox, and with one of our lovely and very clever (modified) Genuine BT ADSL Adapter Faceplates. If you need any clarification on that last sentence, then you should probably first read the ADSL Faceplate Guide.

We also have to assume that you have at least a Clue about simple circuit wiring. If you don't then to be blunt you shouldn't be reading this, and you should be paying somebody to do this stuff for you. You know it's the Wise thing to do.

Instruction leaflet as provided with our ADSL extension kits
Here's what goes out with our BT Engineer-issue ADSL extension kits when people order it with a line box other than the original BT one.  It's a handy reference for a lot of the elements of phone extension cabling for ADSL.  Bear in mind that any specific wiring and terminal designations are relevant to the sockets and modules we supply on this site.

ADSL_Extension.pdf

Changing existing extension wiring at your NTE5
from its standard faceplate onto a new
(Clarity modified version) BT ADSL Adaptor Faceplate

There are five "IDC" terminals on the back of our modified BT ADSL Faceplate.  If you're simply straight replacing the original NTE5 faceplate with the ADSL adaptor faceplate, here's the connections.


Here's a simple and straight to the point paragraph:
If you already have a phone extension cable(s) connected to the original faceplate on the NTE5, then for the line pair(s) on which you don't need ADSL to be served just move those wires over exactly as they are.  2 to 2, 3 to 3, 5 to 5.  Those telephone extensions are now ADSL filtered.  If ADSL does need to be present on any of those extensions, then you'll want to connect those line pairs to A and B instead of 2 and 5.  That's it, that's your basic briefing.


Now to explain in more detail.  Fetch a coffee.

2, 3 and 5 are for connecting any telephone-only extension wires.  2 and 5 are the "line pair" and 3 is the ringer wire (sometimes called the "bell" wire - if you existed before 1990 you'll remember phones used to have actual tring-tring bells)

Terminals 2 and 5 provide an ADSL Filtered line, which means the ADSL band has been cut off so that it doesn't cause noise on telephones, upset modems in Sky boxes, alarm panels and such.  Any wires connected to 2 and 5 cannot serve ADSL.  Connect extension wires here which will serve ONLY telephony based equipment, such as, if you'll excuse me almost repeating a recent sentence; telephones, faxes, Sky, alarm panels and anything else which ISN'T a DSL service.



Existing cable or new cable?
For DSL carrying extensions, use "twisted pair" cable, preferably Cat5 rated.   Don't argue with me on this.

Your existing cable will of course carry your ADSL signal - but how well it carries it is another matter.  If it's old and knackered, expect trouble.  If it's the accursed physically flat cable famously seen in off-the-shelf , plug-in telephone extensions, expect trouble.  But of course, if you already have some nice, good condition, twisted pair cable, carry on and it should serve you well (assuming it's not badly routed relative to RF interference sources like mains cabling and stuff but that's for a different page...)

Some clarification/explanation about "filtering".
If you're curious or, like me, need to know these things in order to get a decent night's sleep, here's why you need to filter stuff when you have ADSL.

Do please have a read of that link if you don't already know this stuff.  But to sum up in the context of extension wiring, such as is this page's function, then here's the quick facts of it;

When ADSL is activated on your line, the frequency band from 4KHz to approx 1.1MHz is occupied by your new ADSL signal. Any normal telephony equipment will be capable of "hearing" up to around 7KHz, and thus will experience a lot of new "noise", "interference", whatever you want to call it. Filter products chop off everything above 4Khz, restoring clarity to the line for those lower frequency devices. By the same token, without filtering, your voice telephony devices can overlap upwards into the spectrum used by ADSL and can reduce performance there - sometimes as much as causing a dropped connection.

The other side of the coin with filtered sockets is that, obviously, since the ADSL frequencies from 4KHz upward are now killed on that socket, you can't use them for ADSL!
So the reason for this whole splitting/filtering thing is to allow both ADSL and voice services to work on the same single telephone line at the same time, without annoying each other.

Using a single cable to carry multiple extension pairs for ADSL and filtered telephony devices:
You can in fact quite safely use just a single cable for extensions to carry BOTH ADSL/unfiltered AND Telephone/filtered wiring to your ADSL socket(s) and voice equipment sockets around your home/office/garden-shed/secret-underground-lair. The cable MUST be good quality and MUST be twisted pair format. That means NOT £2.99 telephone extensions formerly sold in Woolies.

This is really simpler than you probably think. Filtered voice extensions typically require 3 wires, including the ringer signal wire. UNfiltered ADSL extensions require just 2 wires, although depending on your configuration at the extension locatio you may still need the ringer wire. Therefore if you use a cable which has at least 5 wires in it, you can route a "dual purpose" extension to wherever you choose.

The matter of the "unbalanced" ringer wire is one of some speculation.  The ringer wire in extension cabling might be able to act as a slight RF aerial, introducing noise onto the line pair.  While telephony equipment could not care less about this, a little bit of unwanted RF in the band where ADSL operates is best avoided for obvious reasons.  This can't happen if you're using the BT ADSL adaptor on the NTE5, but another theoretical (but as yet unobserved in the real world) effect might be to introduce a small amount of RF noise onto the line pair when in the ringing condition.  Countless installations use a five-wire single-cable deployment with no observed problems in actual service, but I think it's worth considering at least the theoretical possibilities.  Ideally, you might want to try to create an extension installation without it, and provide self-ringing phone sockets at ADSL extension locations.

Pay up
Right, now that you know exactly what you're doing, let's see the colour of your money. THIS LINK will take you to the main page for these gadgets, whereupon I should hope you'll be ordering some. Come on, spend those mint-leaves, you know you want to.