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Author Topic: New BT Bell Wire Filter  (Read 22558 times)

setecio

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Re: New BT Bell Wire Filter
« Reply #15 on: January 12, 2008, 01:20:54 PM »

Interesting test of these new Bellwire filter faceplates back in May07 ... 6th post on this page >
http://yarwell.blogspot.com/

So these bellwire filters stop interference of the same frequency as adsl (picked up by the bellwire running around the house like an antenna)  passing back through the mastersocket and onto the 2 wire line.

Whereas the adsl faceplate filter stop the same happening with the bellwire and the other 2 wires, but the other 2 wires should be twisted pair and should thus be minimum.
« Last Edit: January 12, 2008, 03:38:53 PM by setecio »
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kitz

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Re: New BT Bell Wire Filter
« Reply #16 on: January 13, 2008, 02:22:47 PM »

>> nteresting test of these new Bellwire filter faceplates back in May07

Good linky - :)
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Ezzer

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Re: New BT Bell Wire Filter
« Reply #17 on: January 21, 2008, 01:03:46 AM »

Typicaly a broadband fault is caused by some of the internal wiring after the master socket / nte. and usualy this is caused by the bell wire (no. 3 on the socket/face plate). When on a broadband fault I would test to the wiring as is, then to the test socket behind the faceplate. If i get a significant difference in the test result between the two the first step is to dis (disconnect) the bell wires.
If this does the trick then the end user gets the option of either leaving the bell wire disconnected, so unless microfilters were in each socket with equipment plugged in then nothing would ring beyond the master socket on an incomming call. or the full adsl ssfp (service specific front plate)
Recently we have the choked bell face plate. If fitted as a retro fit the flap at the front is a slightly off white, marginaly grey colour, otherwise ant nte5 with the "openreach" logo has the choked plate. Thery're quite new so not many have been fitted so far. the main way if id'ing them is a smell cylindrical lug on the inside of the face plate about 5mm across, 10mm high.

If you have an issue with the quality of dsl service, then find the master socket/nte. if it is an nte5 ( a seam running about halfway down, across the socket) take the face plate off & either plug your router/modem in the test socket underneath or disconnect the wires in no.3 (usualy thie wires here should be orange with white hoops but note what wires are already connected here just in case the're different). If you get a good result then leave the bellwires disconnected (although as I stated earlyer you'll need microfilters in any socket with equipment plugged in in order for them to ring on an incomming call.
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soms

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Re: New BT Bell Wire Filter
« Reply #18 on: January 22, 2008, 07:23:53 PM »

The sockets seem to have been a different colour noticable since they have been RoHS compliant but perhaps longer...
Certainly the RoHS Openreach branded ones and the former BT ones are more of a beigh colour that the older white ones.

I am guessing your a CSE ezzer?
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setecio

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Re: New BT Bell Wire Filter
« Reply #19 on: January 28, 2008, 02:59:10 PM »

If you get a good result then leave the bellwires disconnected (although as I stated earlyer you'll need microfilters in any socket with equipment plugged in in order for them to ring on an incomming call.

I thought I read that all modern phones can ring without needing a microfilter, so if your telephones are reasonably new they will still ring anyway? is this true or do they all still need a microfilter if the bellwire is disconnected ?


I have read cat5e is a good way to wire telephone extensions but reading this http://www.diynot.com/forums/viewtopic.php?t=69574 it was pointed out :
A:cable type wise its best to use BT spec CW1308 cable.
B:Or even cat5 cable
A:i'd disagree, the aim for best broadband performance should be to use the same cable that BT use so that the characteristic impedance will be the same.

Now this would say 'don't use cat5 or cat5e but use CW1308 to keep impedance the same'
Is this true ?

The main argument for a filtered NTE5 faceplate on the mastersocket seems to be to isolate additional interference induced on the speech and ringing pair (2&5).
If cat5e is used for the telephone wiring, is this an alternative way to almost rid this interference ? or is the argument above about impedance important ?

Is 1 pair (yes 1 twisted pair) cat5e available.
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roseway

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Re: New BT Bell Wire Filter
« Reply #20 on: January 28, 2008, 03:31:34 PM »

Quote
I thought I read that all modern phones can ring without needing a microfilter, so if your telephones are reasonably new they will still ring anyway? is this true or do they all still need a microfilter if the bellwire is disconnected ?

All POTS equipment (phones, faxes, Sky boxes, etc.) have to have a filter between them and the incoming line pair. So if you haven't got a filtered master socket faceplate then you have to use a filter on any socket which has POTS equipment connected.

Concerning the type of cable to use for extensions, I don't know the answer for certain, but I doubt if there would be much if any discernible difference between CAT5, CAT5e and CW1308. My reason is that ADSL frequencies are pretty low in RF terms so the characteristic impedance is not a big factor.
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soms

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Re: New BT Bell Wire Filter
« Reply #21 on: January 28, 2008, 04:04:50 PM »

Quote
i thought I read that all modern phones can ring without needing a microfilter, so if your telephones are reasonably new they will still ring anyway? is this true or do they all still need a microfilter if the bellwire is disconnected ?

A microfilter is required to keep the ADSL frequencies from reaching the telephone equipment. A microfilter is not required in a socket which is not carrying broadband.

In non-broadband installations the ring wire should be connected and since the release of the bell-wire filtered NTE5 front plates there is really no need to disconnect it.

With regards to ringing...

Most, nearly all new telephones are two-wire phones. This means that they do NOT need the ring wire to ring.

Even with the ring wire connected at the socket, most phones use a 2-wire cord which doesn't carry the ring current.

These modern phones incorporate an internal ring capacitor in the same way as an ADSL microfilter does.

Old telephones definitely do use the ring wire. Examples are all the old GPO telephones and older BT telephones.

In these cases, where the ring wire has been disconnected, if the phone is plugged in to an extension socket directly, it will not ring.

Plugged into a microfilter it will work fine. Plugged directly into the master socket front plate or the test socket, it will work fine as the ring wire is connected internally at this point.
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setecio

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Re: New BT Bell Wire Filter
« Reply #22 on: January 28, 2008, 05:59:36 PM »

Thanks for that. Yes, I was thinking in terms of cutting the ring wire and then moving house in the future, but forgetting to reconnect it. The new owners would probably have new enough phones that would just work, and if not they would probably think the phone is broken and try a newer one, thus fixing the problem quickly without BT being involved. So cutting the ring wire shouldn't really be much of an issue.

If cat5e was used for the telephone extension cable, would it still act like a big antennae for noise in the same way that CW1308 does ?
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roseway

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Re: New BT Bell Wire Filter
« Reply #23 on: January 28, 2008, 06:49:03 PM »

Quote
If cat5e was used for the telephone extension cable, would it still act like a big antennae for noise in the same way that CW1308 does ?

Both CAT5e and CW1308 are twisted pair cables, i.e. each data pair is twisted together. This substantially reduces interference pickup because most of the interference is picked up equally on both wires, so there's no voltage difference between the pair of wires. It's not perfect of course, so even twisted pair cables will pick up a little interference, but it's quite a small amount. Without looking at the specs I suspect that CAT5e is the better spec, but as I said, I doubt if it makes much practical difference.
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  Eric

setecio

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Re: New BT Bell Wire Filter
« Reply #24 on: January 29, 2008, 10:18:50 AM »

Since new phones can now ring without the presence of a ringwire, and householders desire for wires to be 'hidden' I'm surprised that single pair CW1308 (and cat5e) has not appeared in mass on the market. I would imagine it would be a thin cable which is easy to hide.

The filters that are used in this new Bellwire filter and those used for adsl filtered NTE5 faceplates are two way filters, aren't they ? In the adsl filtered NTE5 faceplate, the idea is that the broadband signal does not get through the filter, AND also that any interference induced into the telephone extension wiring, which is the same frequencies as broadband, does not pass back through the filter. ?

Thanks.
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roseway

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Re: New BT Bell Wire Filter
« Reply #25 on: January 29, 2008, 12:57:43 PM »

The filters aren't two way exactly. They do two things: they stop ADSL signals from interfering with the telephones, and they stop the phones from loading the ADSL signal (which would have a big impact on the quality of the ADSL signal).
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  Eric

setecio

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Re: New BT Bell Wire Filter
« Reply #26 on: January 29, 2008, 08:01:29 PM »

If they aren't 2 way, how do they stop the mush feeding back into the line and degrading the adsl signal as described below. I thought an adsl filtered faceplate was more effective than disconnecting the bellwire, but surely it must be a 2 way filter to do this effectively and stop the mush coming back onto the main line and degrading the adsl signal ?

Taken from 'adsl tweaking' here http://yarwell.blogspot.com/2005_08_01_yarwell_archive.html

Quote
In my case, the ring wire runs around my house as part of the feed to at least 6 extension phone points, in doing so it acts as a nice big aerial (antenna) to collect any radio transmissions and random electrical noise that may be passing through. It then feeds this mush back into one side of the twisted pair through the capacitor that is there to provide the ring signal and consequently degrades the ADSL signal.
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kitz

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Re: New BT Bell Wire Filter
« Reply #27 on: January 30, 2008, 10:36:55 PM »

heh - dunno if its me speed reading  and I may have lost the plot...  but everything everyone has said seems to be correct  :D
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roseway

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Re: New BT Bell Wire Filter
« Reply #28 on: January 30, 2008, 10:54:55 PM »

Quote
If they aren't 2 way, how do they stop the mush feeding back into the line and degrading the adsl signal as described below. I thought an adsl filtered faceplate was more effective than disconnecting the bellwire, but surely it must be a 2 way filter to do this effectively and stop the mush coming back onto the main line and degrading the adsl signal ?

Sorry, I missed this question earlier.
The point is that the ADSL side isn't filtered at all. There is a direct connection with no filtering from the incoming line pair to the ADSL modem or router. The 'mush' which comes from the ring wire is (or was) connected directly to the input of the modem. In fact, BT are now supplying faceplates with filtered ring wires to overcome this problem. But there is no requirement for POTS signals to be filtered out from the ADSL side because ADSL modems and routers are designed to respond only to the defined ADSL frequencies.
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  Eric

soms

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Re: New BT Bell Wire Filter
« Reply #29 on: January 30, 2008, 11:12:20 PM »

Quote
Since new phones can now ring without the presence of a ringwire, and householders desire for wires to be 'hidden' I'm surprised that single pair CW1308 (and cat5e) has not appeared in mass on the market. I would imagine it would be a thin cable which is easy to hide.

Just a quick reply to this...

I recon two-wire would be acceptable on the basis that PBX master sockets were used, phones using ring wires are still out there, and much used, and anyone who put in such an installation would create a fair bit of confusing on that point.

Also, BT is now using 4-wire again (seems to the old colour scheme as well) which is pretty tiny stuff.

Mind you, cable from different manufacturers alone, regardless of the no of pairs can make a big difference. I have a reel I bought which is decent 3-pair with a nice finish sheath which is the size of BT's 4-wire.

Then again, well manufactured 2-wire would be even smaller.

Standard cat5e being unshielded will still act as a ring wire antenna the same as CW1308. The reason being the "imbalance" caused by the utilisation of only one wire in the pair, even though the cat5 has more twists it will behave in a similar way.

As long as it is twisted pair and solid core (not that nasty alarm wire or mutli-core stuff) it should be fine.

The 4-wire colour code is like so:

Pair 1 - solid blue and solid orange wires
Pair 2- solid green and solid brown wires

Blue - same as blue/white - terminal 2 (Line B leg) on LJU
Orange - same as white/blue - terminal 5 (Line A leg) on LJU
Brown - same as Orange/white - terminal 3 (ring) on LJU
green - same as white/orange - terminal 4 (spare/earth) on LJU

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