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Standard User derby13
(regular) Sat 04-Apr-20 21:58:05
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Slow speeds and bridge tap


[link to this post]
 
Hi all. I've had my mum on the phone complaining of slow internet. In the absence of being able to go over and check it out for myself at the moment, I put her phone number into the BT DSL checker and a couple of things looked odd. Here's a screenshot: https://i.imgur.com/3Y0Hfbi.png

Firstly the max observed speed is a lot lower than expected, even below the handback threshold. Secondly I noticed that the bridge tap status is Yes. I've never known this before, only ever No or Unknown. Can someone fill me in on what this might mean? I've done a bit of googling, and from what I can gather it involves a single line serving multiple houses, and signals being reflected back causing errors, but to the best of my knowledge there's nothing like that. Unless there's part of an old setup still connected somewhere? It's an old house so the line has been in for several decades.

I've told her to report to BT, but just interested in what we're dealing with here.

Cheers all.
Standard User MHC
(sensei) Sat 04-Apr-20 22:22:02
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Re: Slow speeds and bridge tap


[re: derby13] [link to this post]
 
What you have seen is teh origins of a "bridge tap" these days it can mean having an extension run off teh line well before the filter/splitter and modem.

The signal travels down the tapping (spur) and is reflected back. At some frequencies it is in phase, at others, out of phase by 180 degrees and everywhere in between. Te length of te tap defines the frequency response so every one is different. When in phase the signal has little degradartion, increasing and increasing until 180 degrees or inversion is reached and at that point teh signal is totally negated resulting in several tones being unusable. If you look at a bits/tone graph, a brdge tap will show up as a notch and there will also be harmonic repitition of it.

So, EXACTLY what is teh layout of teh house ... how many sockets, and hwo are they all connected?


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User MCM
(knowledge is power) Sat 04-Apr-20 22:29:40
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Re: Slow speeds and bridge tap


[re: derby13] [link to this post]
 
A bridge tap is often where extensions, or rather the cabling to extensions, are wired incorrectly and can considerably reduce observed connection speeds. A bridge tap can be as simple as the incoming line being split and terminating in more than one socket rather than at a single master socket with any extensions then wired to the master. Internal wiring is the customer's responsibility and is a chargeable repair however being on the customer side repairs can be carried out by others than BT.


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Standard User burble
(committed) Sat 04-Apr-20 23:14:22
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Re: Slow speeds and bridge tap


[re: MHC] [link to this post]
 
When a bridge tap shows it doesn't automatically mean it's inside a property, we have had a bridge tap show several times, and each time it has nothing to do with the internal wiring as we only have a master socket with no other internal wiring.
Standard User derby13
(regular) Sun 05-Apr-20 11:51:52
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Re: Slow speeds and bridge tap


[re: MHC] [link to this post]
 
The incoming line just goes to the master socket with no extensions running off it. It's a single socket NTE5 with a plug in microfilter which has the router and a single landline phoneconnected.
Standard User Zarjaz
(eat-sleep-adslguide) Sun 05-Apr-20 12:54:16
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Re: Slow speeds and bridge tap


[re: derby13] [link to this post]
 
Then that should be an ideal set up ... and wouldn’t normally give the ‘bridge tap’ test result.

There, as another poster points out, times when ‘bridge tap’ shows as a test result, when in fact one doesn’t exist ........ but this is very rare indeed.

Openreach are not currently working within customer premises during the Covid-19 pandemic (except in exceptional circumstances) So raising a fault will get the line checked out to the nearest readily accessible point to the property.

Edited by Zarjaz (Sun 05-Apr-20 13:30:31)

Standard User dect
(experienced) Sun 05-Apr-20 13:28:07
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Re: Slow speeds and bridge tap


[re: Zarjaz] [link to this post]
 
smile

Edited by dect (Sun 05-Apr-20 13:36:38)

Standard User Zarjaz
(eat-sleep-adslguide) Sun 05-Apr-20 13:31:06
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Re: Slow speeds and bridge tap


[re: dect] [link to this post]
 
Edited - ta

Standard User derby13
(regular) Sun 05-Apr-20 18:32:43
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Re: Slow speeds and bridge tap


[re: Zarjaz] [link to this post]
 
OK, after speaking to the folks over the phone today, it turns out I'm wrong about the setup, and I think I've found the answer to the issue.

There is indeed another phone socket in the house, in a spare bedroom upstairs. This has clearly been wired up incorrectly however. The dropwire goes into the junction box under the eaves, and from there it actually splits two ways - one cable to the socket in the hallway, and then another cable (again directly from the junction box) to the upstairs socket! (Not used and installed before they moved in). They don't have anything connected to it, but clearly this is the bridge tap and presumably the cause of the slow speed.

Where do I stand on sorting this out? I suppose cutting the wires at the junction box, though not technically touching the OR network, but just disconnecting the unauthorized spur, would not be allowed as it's before the official master socket. I suppose if we got them out to sort it, it would be chargable?
Standard User Icaras
(experienced) Sun 05-Apr-20 19:12:14
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Re: Slow speeds and bridge tap


[re: Zarjaz] [link to this post]
 
In reply to a post by Zarjaz:
Then that should be an ideal set up ... and wouldn’t normally give the ‘bridge tap’ test result.

There, as another poster points out, times when ‘bridge tap’ shows as a test result, when in fact one doesn’t exist ........ but this is very rare indeed.

Openreach are not currently working within customer premises during the Covid-19 pandemic (except in exceptional circumstances) So raising a fault will get the line checked out to the nearest readily accessible point to the property.


I’ll take your word for it. I never once saw that myself.

I was incredibly confident in that “bridge tap” test result whenever I saw it even if I couldn’t find the actual culprit sometimes, maybe it was buried behind a wall or that sort of thing. If I couldn’t locate it I’d run a new lead-in entirely straight into the master socket and that would then return a normal test result.

The only time I can think that there would be a bridge tap in the network would be if they’re doing a cabinet changeover, and then that’s something done on purpose just while they’re wiring up the replacement cabinet and is temporary. Very rare though also.

In reply to a post by derby13:
Where do I stand on sorting this out? I suppose cutting the wires at the junction box, though not technically touching the OR network, but just disconnecting the unauthorized spur, would not be allowed as it's before the official master socket. I suppose if we got them out to sort it, it would be chargable?


That’ll definitely be what’s causing the reduced speed. You could cut the spur off at the junction box (BT18 or Above Ground Closure) certainly and that would sort it. Only concern there would be if you just cut it you’re leaving a stub of wire there that could corrode and cause problems, so I suppose it depends how well you think the junction box is doing keeping moisture out.

Icaras

Edited by Icaras (Sun 05-Apr-20 19:16:29)

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