Whilst browsing the TLC web site, I found a "broadband enhancer". It doesn't say much about it other than it has a bell wire filter.
Now when I ran some extention sockets, a BT engineer told me to cut the bell wire as he said it could pick up or radiate (can't remember which now) interference.
I'm afraid I didn't listen and ran 4 core wire. I know most phones don't need the bell wire but I thought it best to leave it for compatibility. Perhaps I would have been better with 2 core cable?
The range is here:
formatting link
do they work? Are they any good? Is it filtering interference from the bell wire? I thought the twisted pairs were supposed to make the cable immune to such things?
I note that a new master socket is cheaper than the add-on, but aren't only BT supposed to change the master socket? If so, why are they for sale to everyone? Would you buy the add-on or change the whole thing? Or would you not bother at all?
Would using 2 core cable mean that such things are not needed?
Finally, it says new NTE5 master sockets have this built-in. How do I know if mine already has this?
Replace the master socket front panel with one of these.
formatting link
any extension wiring on 2 & 5. Don't bother with the bell wire on terminal 3.
If you plug your router in to the master socket, you simply plug it into the new faceplate, dispensing with all micro-filters. If you router is remote, then you need to cable A & B to the router's location.
You can always disconnect the wire - having spares in the cable is not itself a problem.
formatting link
> How do they work? Are they any good? Is it filtering interference from
That is actually the crux of the problem. unlike the A & B wires, the bell (which is derived from the B wire via a capacitor in the master socket) is unbalanced, and twisted together with the earth break recall wire which is typically unused.
However there are other situations where one might want install a master socket on private PABX systems for example.
The add on, one could argue is ok for the end user to install - since it does not involve access to the BT side of the wiring.
I would probably just disconnect wires except 2 and 5 at the master socket for any extensions. If you find a phone that does not ring on one of those extensions then either plug it in via a microfilter (to regenerate the bell signal locally) or add a bell capacitor to the socket wiring, or swap the socket for a PABX Master socket.
Using 2 cores means they are not needed. Same applies to using two of your four cores.
When was it installed? Unless it was the last couple of years, then it probably does not.
Twisted pair does - the problem is the ring signal on pin 3 isn't part of a pair and acts as an aerial picking up interference which it injects onto the signal pair.
The simplest (and most effective) solution is simply to disconnect pins 3 and 4 in EVERY socket so you only have pins 2 and 5 connected throughout.
Into each socket you use plug an ADSL filter. As the ADSL filter incorporates a ringing capacitor it restores the ringing signal (still needed by many modern phones). Everything works, no RF pickup, speeds as high as you can achieve and nice and simple.
> How do they work? Are they any good? Is it filtering interference from
The sockets for general sale do not have the BT or Openreach logo moulded into them so it is obvious if you have changed it! The newer socket (unofficially known as NT5A) has a small cylindrical moulding on the back of the removable faceplate that prevents the add on being fitted. The moulding contains an electrical filter component that reduces interference. There is no problem with having used core cable.
Didn't BT run trails years ago(*) and found that multiple ADSL filters is a not a good thing?
Far better to have a single good filter at the NTE and run conventional extension wiring from that for ordinary phones. The bell signal should be derived post the filter or just use a single pair and fit master sockets everywhere.
(*) About the time they where abandoning sending an engineer when some one oderd ADSL and went down the self install route.
No, multiple ADSL filters have no cumulative effect.
The ADSL filter spec requires a ringing capacitor (albeit with a REN of 2 rather than 4). Whether you use a master socket or slave is immaterial as the filter supplies the ring signal in any case and doesn't have pin 3 connected.
Having an ADSL faceplate can be tidier if the master socket and computer/router are near the master socket but in many installations the master socket is in the hall and the computer in a bedroom.
My broadband was an engineer installation with the PC remote from the master socket. The engineer put the ADSL socket near the PC and wired it from the original master location. He then then used a pair in the cable to wire back to the original master location where an ordinary socket provided the interface to existing extension wiring.
In that case, I would still use a master faceplate filter, choosing one with unfiltered A and B line connections on the back as well as the filtered phone connections on 2 and 5, such as
formatting link
Connect all the house phone wiring to the filtered connections on the back of the new faceplate except the one, single twisted-pair carrying the ADSL signal direct to the computer room. There, fit an RJ11 socket for the router or, if a phone is also needed, use a filtered slave socket such as
I see. Not that it matters because interference is interferences, but where is the interference coming from? Is it off the line or externally from electrical noise in and around the house?
Does this noise then travel back to the master socket to the circuitry that creates the bell signal and thus onto the line?
Yes, that's what I am thinking now. Or if someone was to wire from scratch only use 2 wire/1pair cable.
I never knew either of those: that modern phones still needed the ring signal or that the filters recreated it.
If every socket has a filter, doesn't that filter out the interference though? Why is disconnecting pin 3 still necessary? Doesn't the filter work on this type of noise?
Is the problem with this that it then ties you to have your router in one room? At least with plug in filters, you can move the router from room to room if needed? For example, I recently moved my router into another room whilst redecorating. I couldn't do this if it had to be in the room with the master socket.
Also, if the master socket is in the hall and you have to run the broadband from the master socket, can these new A&B wires pick up interference over a long run, or does the twist prevent that?
Yes - you have a twisted pair cable which cancels out noise because noise is picked up equally on both cables in the pair. If you now connect a separate cable to one line of the pair you remove the inherent noise canceling capability of the pair.
A significant number of modern phones still require a ringing signal on pin 3.
The ADSL filter (contrary to its name) filters absolutely nothing on the ADSL side of things. Its purpose is to stop the ADSL signal interfering with the audio side and the audio side loading the ADSL signal too much. It should really be called a "not ADSL" filter. Radio frequency noise introduced on the wiring is not filtered from the ADSL channel at all.
Some of the newer face plate filters have both filtered connections for the non ADSL extensions, and also the unfiltered (although surge arrested) exchange pair to enable you to run ADSL carrying extensions as well. As they are a balanced pair, they do not suffer the noise pickup roblem of the ring wire.
Can be all sorts of sources - local noise picked up from appliances and the mains, or HF radio broadcasts being picked up. It can even pick up continental radio signals - especially during the night!
The "circuitry" that creates the bell signal is just a lone bi-polar capacitor. As is the nature of capacitors they block DC but allow AC signals to pass. Hence the interference is allowed straight through to the ADSL carrying exchange pair.
(the historic reason for the ring signal being derived from the main pair onto a separate wire via a cap in this way is so that the DC switching on the line when the phone goes on an off hook, and also the pulsing from old pulse dial phones, does not cause the ringer bell to "tinkle" in other extension phones)
You could - or just leave a pair spare.
Some phones need it, some don't. No easy way to predict without trying.
The filter is actually a low pass filter, active only on the audio part of the signal. Contrary to popular expectation, its primarily there to prevent the audio and DC switching (which can have HF noise associated) interfering with the broadband, rather than the BB affecting the audio[1]. If you pickup and replace the handset on a phone attached to an unfiltered connection on an ADSL line, the modem will often lose sync and have to reacquire it.
The ADSL connection on the filter is frequently just a straight through connection to the main line pair.
[1] The ADSL signal is well out of audio frequency range and hence not audible (or reproducible by the cheap audio components used in phones). Although on some rare occasions you will encounter some phone equipment that will due to a quirk of its design partially demodulate, or frequency shift some of the BB signal and acquire a background hiss without a filter.
I will disconnect the bell wire on my extensions. It seems that will have the same effect as a new face plate but without the cost.
I was interested in your comments that the adsl is never filtered. Is it that this new face plate is only filtering the interference from the bell wire rather than filtering the adsl itself?
Is there any advantage to ever filtering the adsl or is the line from the exchange also a twisted pair? Is it that filtering is never necessary?
I think I have heard the hiss you mentioned on phones that aren't filtered (not in my own home!)
Probably not. The modem filters out the noise to extract the signal. If it can't filter out the noise using its DSP there is no reason to expect an external filter to be significantly better.
The filtering of the face plate is different, it stops some of the interference from getting on the line in the first place.
The normal ADSL filters are there to stop someone screwing up the line conditions when they pick up a phone, if they did the modem would have to re-train which can take several seconds. The filters do no stop the ADSL from interfering with the speech as there shouldn't be any in the first place.
If you have radio frequency break through and are getting noise on the speech there is a fault somewhere and fixing the fault is more likely to work than trying filters.
ADSL signals are way above the hearing of any human and something else would have to be converting them for you to hear them. There should be nothing that does that in a telephone.
I always locate the router as near as possible to the master socket. If your computers are in another room then run ethernet cable(s) from the router to the computer, using a separate switch if necessary.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.