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Cable types & their suitability for ADSL


A wide variety of cable types are available and it is often difficult to know what type of cable is best suited to a particular task. In this article we explain the types of cable available and where they should be used.

Telephone Cables

For most people the most important part of an ADSL installation and indeed the one that has the biggest potential to impact performance is the the telephone cabling. Clearly the end user has no control over the cabling from the exchange to the entry point of the premises as this is all provided by BT Openworld. However the cable used on the internal telephone extension wiring and the cable used to connect the modem to the ADSL service are the users responsibility and often the biggest cause of connection problems. Using the wrong cable can considerably degrade the performance of ADSL.


The incoming cable is typically terminated with a BT NTE-5 Master socket that marks the end of BT's responsibility and the beginning of the subscribers responsibility. So any wiring from this point on should be investigated to ensure it is of an appropriate standard to ensure a reliable connection.

BT Master Socket

Note:Some older installations may not have a proper master socket fitted and it would be advisable to have the installation upgraded to have a proper NTE-5 socket fitted.

Types of Cable

Flat IPC Telephone Cable FCC68/CW1311

This type of cable is commonly supplied in ready made DIY telephone extension kits; the type that are plugged in rather than require hard wiring. The reason this cable is so common is that it is very cheap and it is easy to install the connectors on the end. Also it is quite popular due to its low profile, making it easy to obscure. Typically the RJ11 cable supplied with a modem is also made from this cable. While the short length of just a couple of meters as supplied with the modem will not usually cause any problems for most people, this type of cable is by far the worst type of cable to use for ADSL so long lengths should be avoided. We only supply a maximum length of 10m for our economy RJ11 cables to avoid problems anything longer would not be recommended. If you are near the limits for receiving ADSL or experiencing problems this type of cable should be avoided altogether.

Non-Twisted Telephone Cable

Most telephone cables that you can buy in a DIY store are not twisted pair. They are cheaper, general purpose low voltage cable as used for house alarms. You often see it labeled as telephone/alarm cable. This cable has straight through connections that have no rejection to interference. This cable is fine for voice but can only be used in short runs in a typical home/office environment where there are lots of sources of electrical interference. It is not a good idea to use this sort of cable for ADSL installation especially if more than 20m of cable is required, it would be best is this type of cable is avoided altogether.

CW1308 Twisted Pair

CW1308 Telephone CableProper telephone cable is twisted pair (the official standard is BT reference number CW1308). It is typically manufactured from 0.50mm solid tinned copper and each of the pairs of wires is colour coded and loosely twisted together. This is the same type of cable that a BT engineer will use if you have them install an extension.

This cable is used for and works well for voice and ADSL as its twisted pair construction provides some resistance to interference. As the CW1308 cable is essentially the same spec cable is used throughout the whole telephone network, it known to work well. A good long run of CW1308 cable can be used for ADSL, 50m can typically be easily achieved without any noticeable degradation. CW1308 is a economical way to ensure a reliable connection and its reliably small diameter means it is not unsightly and easy to pin to skirting boards etc.


Quite often CAT5 cable is recommended as the ideal cable to use for ADSL wiring. CAT 5 cable is a twisted pair cable so it is perfectly suitable for the purpose of ADSL. CAT5 cable is designed for Ethernet networking applications that run at much higher frequencies and higher data rates than those of any variant of ADSL. As a result the wire used is thicker and the cable has a higher number of twists per meter than CW1308 cable as it is required for the higher frequency signal. Similarly CAT6 cable has even more turns per meter and even thicker wire is used to account for gigabit Ethernet speeds. There is very little benefit in choosing CAT5 or CAT6 cable over the standard CW1308 cable as the extra twists will not benefit the ADSL signal. CAT5/6 cable is much bulkier than CW1308 as it typically has 4 pairs (8 wires) and is usually supplied in a grey finish making more difficult to hide. Our recommendation is that if you are already installing CAT5 cable for networking and are able to hide it away then it there is no harm in using it for ADSL extension wiring at the same time as you probably have bought a drum of it and have some spare.

ADSL Nation Pro+

Our Pro+ cable has been specially designed for ADSL Installation where there are problems with interferenc or very long runs of cable. By using a twisted pair wire with the optimum number of twists per meter for use with ADSL, ADSL2, ADSL2+ installations it achieves the best possible interference rejection properties. In order to further reduce interference a foil screen is included. For really difficult situations such as electrically noisy machine rooms our Pro+ Installation cable includes a shielding braid that can be used as a drain wire to safely carry interference to an earth connection.