I’m often asked about phone extension wiring, usually when folks don’t want move their master socket .
Elsewhere I’ve blogged on how to connect phone extension wiring together. But not on the importance of choice of cable.
You might have “Superfast Broadband” to your premises, but this won’t mean anything if it’s slowed down by sub-standard phone extension wiring.
Some suggestions:-
All Cables Are Not The Same.
Just because it makes a circuit and gives you a dial tone does not mean it’s suitable. Broadband pushes non-fibre technology to its limits – it needs the very best in cable.
Solid Copper Core. Not Stranded.
“Stranded” cable is made up of small copper or steel strands – see our photo above. Broadband signals hate it. It attracts interference. It does not connect easily or reliably in professional-grade jointing devices. Burglar alarm wiring uses it extensively, but that does not have to carry ultra-rapid data signals, just simple voltage. Most professional jointing equipment uses a “punch-down” method of connection known as IDC (Insulation Displacement Connection). This only works well on solid copper cable, not stranded. So don’t use it.
Not Everything that Looks Like Copper, is Copper.
Some cheap cable is aluminium, coated with copper, and called CCA, (copper-coated aluminium). It does not carry signals as well as pure copper cable. It breaks easily, and causes infuriating, time-consuming intermittent faults. The copper rubs off at the joints, allowing corrosion to form. BT used this in their network in the 1970s during a copper shortage, and are still suffering the consequences 40 years later. Look for “CCA” on the outer sheath. It will look like copper on the outside, but the core will be a dull silver colour. Like aluminium, coated in copper, in fact.
The Twist, and Why It Matters.
Electrical signals on a pair of wires can “talk” to each other magnetically and slow each other down, usually when laid side by side over a distance. Professional-grade cable has a twist incorporated into each pair of cables – see our photo above.. This minimises interference “crosstalk”. I have seen broadband speed increase significantly by replacement of a flat under-carpet cable. We replaced it with proper solid core twisted pair cable run along a skirting board. The speed went up right away.
Please Tell Me – What Do The Professionals Use?
A search on eBay for CW1308 will lead to the proper stuff. CW1308 is a BT-specification number for the cable they use for voice and broadband cabling. Some eBay traders are selling it by the length, which is very useful if you don’t need a 50 metre drum. Furthermore, a former BT subsidiary formerly called BT Cables (and now renamed British Cables Company) actually supply it, so you can get the very same stuff that BT/Openreach use, via eBay or trade wholesalers. If you’re buying anything else, simply check that it is “twisted-pair”, pure copper, and solid core.
What About Cat 5 Data Cable?
Cat 5 network cable is also suitable, providing it’s not CCA. It’s just a bit awkward to terminate in telephone sockets, as it’s 4-pair cable in a large sheath. It’s designed for data sockets.
If you value your broadband speed…
…don’t carry out phone extension wiring with anything less that the proper stuff. Or get me in to replace it if you’ve inherited it.
Hi, I’ve read most of your articles and they are very intresting for people with very poor knowledge in electrical wiring and cables who like to do their things themselves… i have a question though that has not been answered in any of your articles: can i connect a telephone cable to an electrical 4mm wire in order to extend my cable? If not a simple connection are there any devices that can be used to link that phone cable to the electrical wire? It is good to mention here that these electric cables are not plugged and do not carry electricity, it just happened that these cable exist at the right place…
Hello,
I think I may have addressed this issue by stressing that telephone and broadband cables must have a twist in their pair of wires to function at optimum speed and clarity. Power cables do not have a twist.
You would probably get some level of service, but certainly not the best.
Hi,
I’m trying to joint telephone cable, the drop wire is old BT, the wires are orange, white, green amd black, the only wires used where the orange and white, what colour wire do I joint these to on the new cable?
Hello,
Typically, by convention, blue/white pair are used first in any cable. I have blogged about cable colours elsewhere.
You could, of course use any colour combination, but this makes life confusing for any engineer coming to work on your wiring.
I have written a blog especially on wiring colours, but, this being Sunday afternoon, I am too lazy to look it up. 🙂 Go to the “index” blog and you should find several on wiring colours there.
I hope that this helps! Rob.
Hello, your blog is an excellent source of info on telephone wiring, extremely well presented. I have one question that I have not found the answer for yet – I may not have looked enough.
I have a very old black BT wire entering my house, the wore colours are not banded like most of your illustrations. The wire was recently chopped during the installation of a new front door. I’d like to repair it and refit the master socket using newer white CW1308 wire. Is there a diagram to show the corresponding colours??
Many thanks
Hello,
Thanks for your kind words. The black cable is called “drop wire”. A quick Google will tell you more about it, but in brief, there are normally two pairs of copper wires in it, and around four white-sheathed spring-steel wires which give it support when suspended from a pole. Caution – there are VERY sharp when cut! They usual wiring colour convention is orange and white for the first (copper) pair, green and black for the second pair. If you have only ever had one line into your house, it’s likely that the orange and white are the active pair. Please note that the cores are 0.9mm, whereas normal white-sheathed internal cable is 0.5mm core, so the two don’t punch down reliably together. You may need jelly crimps. I hope that this helps!
Hi Rob
Thanks for the cable information and general information on your site.
I have a cable related question (hope this is the right place for it).
I have to run a 32A 240v ring main, and it will have to run parallel with the incoming BT cable, that connects directly to the Master socket, for about 2m. I can only get the mains cable about 100mm away from the BT cable. Do you think there will be any interference if I do this?
And in general, does higher power mains cabling have any affect on the BT cable signals when in close proximity? Are there any BT guidelines for these situations?
Kind regards
Steve
Hello Steve.,
Three-compartment dado trunking is used extensively within office environments, the main compartment containing ring main cables, and the upper and lower compartments housing data and voice cables. The space between the cables varies around a mean of 100mm, so I think you should be fine.
Opinions of even highly-experienced ex-BT engineers vary on this topic, and I’m not aware of a BT standard on this. The general guideline is to avoid parallel running with mains cables if a all possible – it removes one extra potential source of fault. However, in the real world, this is usually not possible. Therefore, the observation in my first paragraph applies.
I discussed this very issue with an electrician on an installation job this week, and he recalled a situation where an alarm cable gave odd faults. It was discovered that it had been buried in the very centre of a large loom of ring main cables, and some strange induction effect was being caused. As with all data cabling, neat is not always best, when it comes to looming cables, especially mains and data.
In short, I think you should be fine!
Hi, excellent site! I’m currently planning an attic conversion and will include cat6 cable to all rooms. Not sure about adding a telephone cable as well, but I assume I can just have an RJ45 connector on my phone and use the data socket? Thanks, David
Thanks for your kind words. I try to keep ads. down to a bare minimum, but if you can leave some kind words on Facebook or Google, that helps me to justify my time on replies.
Yes, simply (!) crimp an RJ45 plug onto your phone line cords. Alternatively, use an adapter (“Mod-Tap” or “balun”) which connects a BT-type plug into an RJ45.
Cat 6 will be fine for voice. It’s used all the time in business environments.
I’m just about to blog on choice of data cable for domestic applications – one key issue with Cat 6 is, because of it’s central cable divider, the minimum bend radius isn’t as tight, so your curves will need to be more generous and sweeping. This is worth considering if it’s routing via some tight spaces. It’s actually not a bad thing, as Cat 5 is meant to have an absolute “never exceed” radius, but I see it kinked and abused all the time!
Thanks, once again. Rob
Hi Rob , You have a very informative site and I hope you can help a DIY er with a query. I have,from a previous owner, an old never used extension socket fixed on the windowledge in our bedroom. At the weekend i installed a new blind , but had to remove the extension box so as the the blind could drop fully. Thinking that the whole socket was dead I pulled out the wires and taped them up. Now of course i realise that there was clearly a connection as I cant get a line/ring tone on our landline – yet all the sky services are working fine as there is a connection to (what I assume is) the main box in the lounge.
So I thought that just by reinserting the wires with my push down tool all would be fine , but the wires were a bit of a mess and none of the colour codings of wires ive looked at over the internet match up. There are 2 cables coming out of the wall each with orange, brown, green and blue wires. The blue wires out of each cable are twisted together, yet I believe im supposed to insert the blue one ( one of them ?) into pin 2 and the orange one into pin 5 to get working again. They seem to be the old colour codes, no white or blue/white stripes in sight. I’m not sure which colour to put in slot 2 if its not the twisted together blue one. Can you help.
Thanks Mike
Thanks for your kind words. This is hard to diagnose without knowing what is connected to what socket-wise. Some houses are utter cable nightmares, as previous owners may have set up their own colour scheme usage! However, it sound like you might have either very old or very new cbaling (Openreach recently turned full-circle and went back to the solid colours of 40+ years ago. Here’s a quick explanation:-
On some installations of internal extension wiring (post-2012) BT/Openreach have now come full circle and have reverted back to using white four core cable containing solid colours: blue to pin 2, orange to pin 5, brown to pin 3 and green to pin 4 (if used).
(Of course, you should only be using 2 and 5 for broadband and voice)
If you have a multi-meter, you can prove cables by shorting one pair and testing for a short. Also, you could detect 50V DC coming from the exchange.
I hope that this helps.It’s hard to get any further without further information. Much is this work down to methodical proving between sockets and elimination.
Meanwhile, if you can leave some social media feedback, this will help me justify dispensing free advice.:-)
Rob
Your blog has answered several questions, thankyou. Could I ask, what your opinion would be of my plan to lay services for 34m from house to workshop, I planned a 50mm ridged flexible pipe conduit containing alcathane waterpipe, Cat6 network cable, twisted pair phone cable and an armoured 3 core 240v cable.
I’m beginning to think the 240v cable should be buried deeper by 4 inches, but it will still access the workshop over 1m together with the phone and network cables. Will this effect voice and data signals ?
Hello,
Thanks for your comment. I would always use smooth-walled duct where possible, but if it’s having to dodge things, then you have no choice but to use the ridged stuff. Bigger is always better, too! BT standard duct is either 54mm or 96mm.
Remarkably, Openreach publish their guidelines for services distances on-line.
https://www.ournetwork.openreach.co.uk/resources/site1/General/Downloads/quick-guides/Quick_Guide_Duct_Laying.pdf
Note that the diagram shows depths from the surface and apart (see bottom scale).
The last metre should be fine. Remember that offices are filled with dado trunking where 240AC, data, and voice all run together, often (incorrectly) in the same compartment over a distance.
Cat 6 external grade would be my preference. The sheath is much more durable.
If this has been helpful, could you leave some social media feedback, please, as the site has very little advertising! I need to justify my time. Thanks. Rob.
https://goo.gl/maps/p1n9wxi5T6p
http://www.facebook.com/telecomgreen
twitter.com/phone_engineers
Hello Rob.
Thank you for an excellent blog and information that is actually useful! Great stuff.
I have a problem with interference on my phone line after recently installing an extention cable to connect our new garden cabin. There was one exististing extension already there, internal to the house. The interference was immediate. Disconnect the new line at the Openreach master socket end and the interference disappears. In reality, I probably know the what I must do but I thought there may be some tricks or techniques to try before I go re-routing or even re-cabling!
(I should mention that I’m a long in the tooth homeowner with the associated accumulation of knowledge, skills and tools from fixing and maintaining stuff over many years 🙂 )
The new building is 30m from the house but due to location of equipment and services and of course, viable routing options, the extension cable is almost 70m long. I’ve use CW1308 (because I had a full drum of it laying around). I realise that CW1128 or 38 would have been better but the only exposed part of the route is the first 15m where it goes over a NE facing roof, then through trunking, then through ducting and finally clipped along the north facing side of a fence before entering the new cabin. I’ve also run a Cat6 FTP cable along the same route, except for the first 5m because it exits the house in a different place. Unfortunately, for about 15m of the route, the cables run alongside the power sub-main that supplies power to outbuildings. Both cables tested out fine electrically after installation using a cable tester.
The interference is not static / crackle type but rather the “wind howl, whiny, spacey” type. I’ve tried changing microfileters just in case but it didn’t help.
Any hints, advice or tips would be gratefully received.
Thanks again for sharing your knowledge and experience.
Martyn
Hello,
First of all, sincere apologies for the delay in my reply via this page. This was due to a Google security issue.
Sadly, it sounds to me like either a mains interference issue, or damage to the cable causing an earth effect at some point. It’s hard to diagnoise without hearing it, of course.
An “old-school” ex-BT engineer would have a “Tester SA9083” or similar which would verify pair quality. This is a kind of multi-meter which quickly checks basic faults. It may be time to call an independent chap in. Let me have your postcode, and I’ll see if I have a contact in your area.
Hello Rob
Thanks for the reply and for maintaining this very useful blog.
I’m in Cornwall, near Newquay (TR7 postcode)
Thanks
Martyn
Rob, on your reply to “Rob Govier on 4th December 2017 at 10:26 am”, you state that the orange and black are the active pair, I’m assuming you meant orange and white?
Yes, orange and white is correct. Correction made. Thanks for pointing this out. Sorry for the delay in response. This was due to a Google security issue.
What a great informative site. You have the skill of putting your advice across clearly and without the b******t. I wish I had found your site earlier! I recently changed my master socket to find one of my extensions wouldn’t work. I messed about with a different com cable which is slightly heavier (as per the 2nd ext) and all became good, and before anybody posts, no, the old cable wasn’t broken. I could only come up with it being an impedance issue. I will certainly be recommending your site to others. Thankyou.
Steve
Thank-you for your generous and kind words. The problem may have even been a continuity issue with one of the punch down connections. Whatever solved it, I’m glad it worked and that you enjoyed reading the posts.
Great blog Rob, i need to extend my master socket and there’s good detail of how this is done on another of your blogs. My question is about the CW1308 cable, if i only need one twisted pair, then what do i do with the remaining pairs ? Do i just cut them off at both ends ?
Similarly the BT cable coming into my old master socket utilises only one pair (red and white) the other pairs are a right mess and just coiled up like a birds nest should i cut these off ?
Also, would you set up a networking hub in a fuse board cupboard ? All the outgoing 230v cables are enclosed in pvc maxi trunking and the consumer unit itself is about half a meter away from where i want to site the router, patch panel ect.
Thanks for your kind words.
My recommendation is to leave the spare pairs coiled up at each end of the cable run. BT always do this with their incoming cable. If the cable is ever damaged, it is possible that you could swap the service onto another pair as a temporary measure. I have done this for a customer in the past when replacing the cable would have involved major work. Unused spare pairs are your friend!
Regarding the networking hub location;- if there is no good alternative, then siting near 240AC voltages should be fine, but my preference is always to give data equipment all the help possible in staying interference-free. Rob.
Hi, I wonder if you can answer a question that has been bugging me for ages? What is the difference between CW1308 cable and CW1308F cable? I cannot find the answer anywhere, nor can I find a copy of the actual BT standard. Any help greatly appreciated 🙂
Hello! I have no idea! However, these folks might know. They were the cable manufacturing arm of BT, and much of their output was branded “BT Cables”. There are some PDF data sheets on their site, if I recall correctly. I hope that this helps. Rob.
https://britishcablescompany.com/
Hi Rob, thanks for the quick reply. I’ll have a look at the link and if I can find the answer I’ll let you know!
Hi, I wonder if you can help with a slow broadband , openreach came and repaired an open circuit drop cable a few months ago and have connected a green and white cable as the input cable, we use to have a broadband speed of 8/9 meg but over the last couple of months is been stuck at 4 mg is this due to the repair as they are using individual cables from each pair in the drop cable?
Hello,
This use of a separate “leg” of each pair sounds like a bodge to me, a way of getting a working service out of a deteriorating cable. The proper solution is to replace the cable. Meanwhile, do you have a dial tone on your landline phone? Lack of dial tone, whilst having a working broadband service at half-speed or less, means that one leg of the cable is disconnected (failed). If no dial tone, report this to your provider.