Thursday, June 01, 2006


Update on phone wiring for ADSL.

BT have introduced "MaxDSL" services which give "up to 8M" depending on line conditions. These services are "rate adaptive" which means the speed achieved by the modem depends on the line condition - a good short line will achieve 8128 kbit/s downstream and the longest poorest line will either drop to 160 kbits/s or fail to connect. In general this means people are getting faster speeds with Max than before, as the previous limits were conservative.

Getting your wiring in order with Max could give you faster download speeds and higher reliability (less errors), and it is worth doing this before changing to Max so the initial training period reports your line at its best. If your attenuation is 35 dB or less you should get 8M, falling to 2M around 60 dB although some have achieved 4M at this distance.

The best option for wiring is to have a filtered faceplate from or fitted on your NTE5 master socket. If you don't want your modem or router next to the master socket you can run an unfiltered extension line from the back of the filtered faceplate.

If you don't have an NTE5 master with removable faceplate it should be possible to get BT to fit one for about £30. Some people have achieved this for free, others have been quoted over £100 - its at the bottom of this page at £30. Probably best to call 150 and say you "want to wire up a permanent extension and you don't have a linebox to connect it to". Don't mention broadband, for simplicity. They won't fit a filtered faceplate, just an NTE5 for you to fit one to.

If you don't get an NTE5 then removing the ring wire / bell wire from terminal 3 of your master socket will get most of the benefit. Since writing the original item I have found a couple of installations where it was necessary to remove all of the ring wires from terminal 3 of all the extension sockets to get the results. Bear this in mind if the first one doesn't do it for you.

Please note that the colour codes on cables are for convenience, the blue and white pair is conventionally used for the phone signal on terminals 2 and 5 but you may find the green/white pair being used or the orange/white pair. Other colour schemes may be encountered, including single (solid) colours. The important thing is that you only need 2 and 5 for the phone to work and that the same colour should be used on the same terminal of each socket.

Finally, remember that removing the ring wire reduces noise on the line but you still have to filter every phone/fax/sky box/alarm/56k modem to avoid them interacting with the ADSL signal. A filtered facaplate removes the need for separate microfilters.

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