The Ring or Bell wire is a leftover from earlier telephone technology but is still part of new BT line installations.
Older phones did not ring on an incoming call without a separate wire carrying a signal to make them do so. Even a few modern phones are the same. The master socket contains a capacitor that generates the signal and sends it up the Ring or Bell wire attached to Terminal 3.
Note that there is a ring wire for each wired-in telephone extension. If there are no extensions there should be no ring wire, but if you are not the first inhabitant of the property it is always worth checking as below in case there used to be extensions that have been removed but the wiring left in place.
Plug-in phone extensions also normally contain a ring-wire. So if you use one of those make sure you read the bit about them near the end of the page even if you have no wired ones.
The problem with the ring wire is that it acts as a long aerial. It picks up noise and feeds it onto the line at the master socket. This can cause a permanent loss of connection speed of typically 500-1500kbps, and I have seen several where it caused a loss of well over 2Mbps.
Solutions to the problem.
The latest BT Openreach logo’ed NTE5A master faceplates have a ring wire filter built in to stop the noise being fed back onto the line. There shouldn’t be a problem.
If you have a relatively modern BT NTE5/5A faceplate without the OR logo but with the BT Piper logo or earlier, where the bottom half can be removed after undoing two screws (which you are allowed to do but be careful as any extensions should be wired to it), then have a look inside. But before you do that, if you would like to see the potential improvement from what I suggest below first disconnect from the net, reconnect, and read the line stats. (See here for help if you need it).
This picture, courtesy of thinkbroadband, shows the back of the faceplate with extension wires attached, and the Test Socket in the backplate on the wall. Do not try to get at the BT wires coming in at the back connected behind the test socket.
Once you have the faceplate removed, connect the filter to the test socket on the wall at the back, reconnect to the internet, and read the stats again. The main figures to note are the downstream and upstream connection speeds, noise margins and attenuations.
If the downstream connection speed is very close to the reading after the immediately preceding reconnection then there may be little to gain from doing anything. With luck it will be noticeably higher and that is the speed we want to achieve in normal usage. If it isn’t, make sure no extension telephones work! If they do they are incorrectly wired and that needs looking into as it will almost certainly be degrading your broadband. (Remember if there are no extensions we don’t really expect any improvement).
Nearly all modern phones contain the circuitry to ring without that signal being sent. All they need are the two signal connections on Terminal 2 and Terminal 5.
Terminal 4 is sometimes also connected, seemingly these days just to provide a tidy parking space for the fourth wire. In the past it was an earth connection used with some private branch exchanges for recall of the operator and in some cases to allow party lines - superceded by DACS. It is now completely unused. (T4 information courtesy of poster “systemx” on the thinkbroadband forums).
If ADSL is in use on the line then as you know everything connected to the line has to go through a filter of one kind or another. All reputable filters also contain the circuitry to generate the ring signal. This means that even phones without that circuitry will ring because of going through the filter.
There are three things you can do.
First and BT Approved is to fit a BT iPlate, also called a Broadband Accelerator. At the time of writing BT Broadband customers can obtain these free (except for P & P) from BT. Others can buy them from several sites. Do a web search for BT iPlate.
It is easily fitted. You remove the faceplate as above, plug the iPlate into the Test Socket revealed on the backplate, then plug the faceplate with its attached wires back into the iPlate which comes with longer screws to replace the originals. (The new screws go through the faceplate, then through the iPlate, and into the backplate. Do not screw the iPlate to the backplate before replacing the faceplate.
Note that the iPlate does not provide an ADSL filter.
For a very informative video and demonstration of fitting it, see this thinkbroadband video, (preferably with sound on).
Second is to obtain a filtered faceplate such as those from ADSL Nation and Clarity. These replace the BT faceplate - again this is allowed. These provide a phone socket and an ADSL socket at the front so eliminate the need for the dangly filter you are probably used to. Much neater.
They contain a built-in ADSL filter and also a ring wire filter.
The drawback with these is that you have to carefully detach the wires connected to the back of the faceplate, making sure you write down carefully which colours go where, and reconnect them to the back of the new one as per the instructions that come with them. To attach the wires you are best to obtain an IDC/Krone tool as used by BT engineers. Cheap versions for occasional use such as this cost from 79p (ADSL Nation) to a couple of pounds or so at places like Maplin Electronics.
Third, and the method used by many, is gently to remove any connections to T3 on the faceplate and make sure they don’t touch any other connections when you replace the faceplate. Don’t tuck them into the hidden space behind the test socket at the back as that is where the main BT connectors are.
Be very careful not to disturb connections to T2 and T5. I advise writing down the colours to each terminal first, as though you were replacing the faceplate with a filtered one above.
Removal of a connection provides 100% filtering!
It may be a little unkind to the next person living there if you don’t reconnect it on moving out. They may have one of the phones that need it and not have ADSL. In which case we can assume they won’t be tech savvy enough to fix it, and a BT callout is expensive.
Plug-in phone extension cables. Most of these contain a ring wire. The best solution is to use an iPlate as above if you have an NTE5/5A faceplate. Removing ring wires attached to the back of the faceplate does not stop these causing your broadband pain.
Some people manage to remove the metal inserts in the plug of the cable (the two centre ones corresponding to T3 and T4). Others stick a small piece of insulation over them. I don’t like the sound of either solution but they seem to work. The dangers are of wrecking the cable and/or the main socket.