Speeding up your ADSL

Qu: If you're finding that you're achieving a lot less than the quoted maximum data rate on your ADSL broadband connection, is there anything you can do to speed up your ADSL service?

Ans: YES, very possibly! It is quite common for the telephone wiring round your house to seriously slow your broadband down. If this is the case, you can do some quite simple things to make it better.

ADSL (Asymmetrical Digital Subscriber Line) is a technology for delivering broadband service using high-frequency signals superimposed on a normal telephone line. Because these high frequency signals can upset ordinary telephones, fax machines, modems etc, filters must be put in the line to these traditional devices, to remove them. However, there are good and bad ways to add filters. Do it the wrong way (the way most installation instructions tell you to!) and you can seriously cripple your broadband performance.

The telephone service that comes to you from the exchange requires two wires. Unlike most parts of the world, we use a three-wire standard for the wiring inside a house, with one master socket and typically several slave sockets. The master socket converts the two-wire service to three wires for distribution round the house. This is not good for ADSL.

Fig.1 - Standard ADSL FilterThe answer is to put the ADSL filter BETWEEN the wires coming in from the exchange and the master socket, so that the high frequency ADSL signals never get anywhere near the 3-wire internal wiring. Unfortunately, the most commonly used filter (Fig.1) cannot do this.

Does it matter? The answer is yes! Ė especially if you have a large house, with several phones on the line. You will not achieve the full speed quoted when you bought your broadband service, and in extreme cases, your ADSL will not work at all. You may also find your broadband is unduly sensitive to interference from other appliances (electronic Christmas lights are reputed to be especially bad!), and the broadband itself may cause interference - for example to your hi-fi.

So whatís the answer? It depends on where you want your ADSL modem to live. If you are happy for it to live near the socket where the service first arrives in your house from the exchange, then much the favourite is to fit an ADSL faceplate to the BT NTE5 master socket (Fig.2) if this is how your telephone service is delivered, or to replace the master socket with an ADSL filtered master socket (Fig.3).

Fig.2 - BT NTE5 Master Socket Fig.2 - BT NTE5 Master Socket Fig.3 - Filtered ADSL socket Fig.3 - Filtered ADSL Master Socket

If however your master socket is by the front door, and your ADSL modem is up in the attic, your choices are not so good. To maximise the speed of your ADSL, you should do as many of these as you can manage:

  • Do not use rotary (pulse) dialling phones on ADSL lines - they may look quaint, but they are not high-speed-data-friendly!
  • Make sure all phones have filters.
  • Use professional filters (Fig.4 - see right), and avoid the ones that look like a 2-way adapter (Fig.1)
  • Disconnect pins 3,4 - usually orange/white - from every socket, leaving only pins 2,5 - blue/white - connected. (If you do this, and you donít have professional filters, you will also need to replace all the sockets with master sockets, or the phones wonít ring.)
Fig.4 - Professional ADSL filter

A note on legal issues

The UK 3-wire telephone house wiring standard was written over 25 years ago, when most phones had rotary dials, and ADSL hadnít been invented, and amazingly, it hasnít been changed (BS.6305, last updated 1992). The phone company (BT or your cable TV company) provides the service up to the Network Terminating Point, which is the NTE5 or master socket, and officially youíre not meant to touch this.

You are also only meant to have one master socket. (Each of the professional filters recommended here counts as a master socket, too.) Having several master sockets does break the transmission rules, and could in extreme cases cause people calling you to experience an echo. However, experience suggests this is not usually a problem. Interestingly, the latest BT Supplier Information Note (BT SIN346 V.2.7 Feb08 - downloadable here) actually recommends this!

If you break the rules, itís most unlikely you will end up in jail. The phone companies only really get upset if you mess something up, and then call out their engineer to fix it!

© Evonet Ltd., 2007,2008.
Last updated: 16Mar08


 

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