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BT telephone wiring, colour codes, common faults & cable quality
April 28th, 2016 11:54 am     A+ | a-
In this post we cover some common BT wiring faults/mistakes, colour code schemes & why cable quality with broadband is VERY important! We also explain the bell wire & why you really want to have the latest NTE5 and most probably a SSFP too (what on earth is an SSFP you ask?! Well read on to find out!!......

Some common faults

Phone ringing continuously
Terminals 2 and 5 swapped between sockets (2 at one socket connected to 5 on another and vice versa)
No ringing
Terminal 3 disconnected

Ringing but no speech (or very poor speech) and can't dial out.
Wire between terminals 2 or 5  broken.

Very poor speech quality, possibly poor bell
Terminal 3 and 2 or 3 and 5 transposed

Colour Codes

BT Openreach are using new cables with new colour codes. The old wiring scheme was as follows :-

Connector 2 - Blue with White Rings
Connector 3 - Orange with White Rings
Connector 5 - White with Blue Rings

This has now changed to :-

Connector 2 - Blue
Connector 3 - Brown
Connector 5 - Orange

The ring wire or bell wire

You have most probably heard of the "ring wire" or "bell wire" & why it is bad news for ADSL & vDSL broadband. Removing the bell wire (pin 3 on the IDC block of the MASTER socket, eg, NTE5) can certainly improve ADSL/vDSL performance if you have internal extension wiring (if you don't have any extension wiring then you shouldn't have a bell wire!). However removing the bell wire is against the BT wiring specification. So what can you do? Well, the good news is BT along with their suppliers cured this problem with the addition of a bell wire filter (or inductor to use the correct term) which is fitted to the latest BT NTE5A socket (which we sell!). In short the addition of a 22mH choke on the circuit effectivily removes the bell wire from the equation while leaving it in place to do what it is there to do!!

So what's the issue? Read on.....

The problem arrises when internal wiring using the 3rd bell wire causes interference, this happens because the circuit is not ballanced, the line pair coming in to your house is what we call twisted pair, the two pairs cancel out any noise on the line, when an extension is added internally the 3rd wire is required to make a lot of phones (most modern DECT phones don't need it) ring (hence the name, ring wire or bell wire-old phones used bells!!) the new inductor cures this while keeping the wiring to specification. Here's the diagram BT Openreach used.....

Bell wire noise diagram

If you fit an ADSL or vDSL  faceplate to an NTE5, such as the NTE2000 or VTE-2015 the problem is also eradicated as the ADSL/vDSL signal is seperated away from the bell wire. BT give these nifty little faceplates a specific term-SSFP's or Service Specific Face Plates.

As previously mentioned the latest NTE5A that we supply feartures an inductor to combat this issue. BT released a product called the BT I Plate (or Broadband Accelerator to use its new name!). The IPlate/Broadband Accelerator does also feature an RF filter however that BT claim can improve line stability-this is the same filter as found in the BT 80B RF3 junction box & similar to the one fitted in the BT Mk2 & Mk3 vDSL faceplates.


These nasty little products reared their ugly heads when the price of copper went through the roof! Customers should be aware of CCS (Copper Clad Steel) & CCA Copper Clad Aluminium) that is being sold elsewhere & wrongly claimed to be CW1308 specification. CW1308 specification requires the cable to be pure copper & twisted pair. A lot of cable that is being sold is also so poorly twisted it could not be described as twisted pair! Less twists = less copper = sneaky savings!! The net result with any of these issues with broadband is degradation in ADSL/VDSL speed, even over relatively short distances! We got caught out ONCE as did our supplier, it seems a pallet of proper cable had CCA mixed in which was marked as CW1308. Obviously the manufacturer  had tried it on (China trying it on?? Really?!!surprise), it hasn't happened since & we work closely with suppliers to make sure it doesn't happen again!

Some of the warning signs to spot this cable.....

(1) CCS is magnetic, pure copper cable is not, grab that magnet & see if a small off cut is picked up!
(2) CCS is a lot stiffer to bend than copper.
(3) CCA is easier to bend than copper, it also lighter.
(4) Cable described as "telephone cable" or "C5" or "C6" rather than CW1308, CAT5 or CAT6.

Some O/T history for you, BT themselves even used CCA when copper was last at silly prices (late 70's/early 80's if memory serves me correctly cool). ADSL didn't exist then but they soon came to realise it wasn't any good with the advent of ADSL! Problems had arisen prior to ADSL anyway, CCA corrodes!

Sadly too late for this customer..........

"Yes can buy cheaper cable ..I did twice , but it didn't work on ADSL 2 . Should have gone to run-IT-direct and used theirs in the first works . If I had , I would have avoided doing the job 3 times over . Excellent customer service , very quick dispatch and good advice freely given ..highly recommended . Anyone want 75m of copper coloured steel cable ? !!"

We didn't gloat, honest yes
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