Bridge tap?

Hi folks.

Can anyone explain what "bridge tap" is please on the availability checker. Image below of what i mean. And the "U" that follows.

http://i66.tinypic.com/2uogvfc.png

Thanks in advance.

Michael.

A bridge tap in terms of an FTTC circuit in the U.K. is when the point where connection to the modem is made is not from the first point on the circuit (ie the NTE) and this point isn't fitted with a faceplate filter if there is extension wiring connected.

It might also mean the line is star wired prior to the effective NTE.

(Can see no image on the link you posted, though that might be the ad blocker on my phone)

The image I see is a normal BT Wholesale estimates table, with the words "Tags: Bridge" above it. The Tags of course referring to the keyword that some search or other has hit so given this image as a result.

What isn't shown is the text that comes below the table so unless people remember that then it is somewhat mysterious . In that text we have the recently introduced explanation of "Impacted" in relation to VDSL.

For VDSL or G.fast Ranges A and B, the term "Clean" relates to a line which is free from any wiring issues (e.g. Bridge Taps) and/or Copper line conditions, and the term "Impacted" relates to a line which may have wiring issues (e.g. Bridge Taps) and/or Copper line conditions.

I don't know what the "U" refers to.

Edited by RobertoS (Mon 15-May-17 08:42:08)

You have your explanation ... At a guess, is your house to exchange around 9km and house to cabinet about 3km?

Thank you for the response Zarjaz,

Easy to understand and detailed response.

Thank you

Michael.

Hi MHC.

To my understanding, no. I've been lead to believe that my line follows a direct path with the road. Given all the mini manholes that are on the grass verge of the route i'm inclined to believe that. But what do i know, i'm far from expert.

So around 3.2km from home to exchange and 3.1km from home to cabinet. By road.

Thanks for pointing that out Roberto.

I assumed that always stayed the same. I'll keep a better eye on the text at the bottom from now on.

Thanks

Michael.

Just going by te speedssuggested by the checker. 3 to 3.5 km usually gives anywhere from 1 to 3 Mbps on VDSL - which corresponds to yours.

However, ADSL2+ with a range of 1 to 4 Mbps suggests somewhere in excess of 6 km maybe up to 9km. If your 3.2 is accurate then there is either a major issue between the cabinet and exchange or it is routed a long way round. Is the cabinet just 100m from the exchange?

Oh i see why you would think that.

Yes the checker is inaccurate. I currently get 8-9 Mbps with ADSL2+. I'm not sure why the checker is so low.

Yes, the cabinet i'm on is very close to the exchange, might even be less than 100m but not certain.

That is what I would expect from ADSL2+ -, in fact pretty good.

Not seen that text at the bottom of the checker before - " Premise environment Bridge Tap Status U"
So difficult to guess what it means, is there any explanation in the text below the checker results? May have to wait for someone with inside knowledge to respond.

Now looking on me mac, and can see the detail ........ I wonder if the 'U' stands for unknown or untested maybe ?

Where is this thing with the U please? It wasn't showing on my iPad and isn't on my Win 10 IE11. Only the wodge of usual bumf part of which I have quoted earlier.

Edit: Not on Chrome either.

Edited by RobertoS (Mon 15-May-17 17:45:34)

See lower left hand of image. There you should see the heading "Premise environment" and in the column to the right "Status"
The line below reads "Bridge Tap" with a U in the next column headed "Status".

Edit: Perfectly visible as part of the image here on Win 10 using any of Edge, Firefox or Chrome.

Edited by deleted (Mon 15-May-17 17:50:54)

Ahhh . Thanks. Mine has an "N".



"Premise" bah !!!!!

"Premise" bah frown !!!!!

I thought youwould like that one whichis why I made certain I copied the text exactly as shown in the graphic.

I suspect that as Zarjaz inimated, U = Unknown, your N = No and there will also be as yet unseen "Y"s for Yes, bridge tapped. Makes me wonder whether OR will react and attempt to correct any Ys.

I suspect that as Zarjaz inimated,(?) U = Unknown, your N = No and there will also be as yet unseen "Y"s for Yes, bridge tapped. Makes me wonder whether OR will react and attempt to correct any Ys.

I feel fairly confident in saying that they will nothing about this unless requested to do so by the CP. Sorting these faults out costs money, money the CP's didn't wish to pay for in the form of engineer installs.

Understood although whether some of those paying next to nothing for their connection will be happy.

My BT estimates have been updated too, with N on the Bridge Tap section.

Clean: High 80 low 65.4 was 66.1
Impacted: High 74.6 low 40.4 was 41.6

Also the ADSL estimates have changed as well but didn't note them, just know they have gone up slightly.

In reply to a post by Zarjaz:

I feel fairly confident in saying that they will nothing about this unless requested to do so by the CP. Sorting these faults out costs money, money the CP's didn't wish to pay for in the form of engineer installs.

You'd hope it signifies a better capability in automatic testing of the line, which can then feed back at the time of sale.

If ISPs can be given a reliable indication of whether the A range or the B range applies, it gives some scope to upsell an engineer install.

You'd hope it signifies a better capability in automatic testing of the line, which can then feed back at the time of sale.

If ISPs can be given a reliable indication of whether the A range or the B range applies, it gives some scope to upsell an engineer install.

Catch 22 though, you cannot make a test for a bridge tap on an FTTC circuit until the service is up and running.

I think it only appears with the telephone number chacker?

Yes.

In reply to a post by Zarjaz:

Catch 22 though, you cannot make a test for a bridge tap on an FTTC circuit until the service is up and running.

I have to admit that I though a TDR - when employed at the exchange end, say, as part of a test head - would highlight reflections from both the main pair and the tap.

Ah - that explains why I couldn't see it here

Think about it ...

As it is referring to a condition on a specific copper pair, it can only be returned on a telephone number check or for a specific line ID.

An address check cannot as there may be multiple lines serving that address.

It shows "N" for our number, which I expected. I presume if it says "Y" then the router is connected to an extension?

I seriously doubt that, and even then surely a TDR couldn't differentiate between those extensions connected after an SSFP or without.

It will certainly highlight the point at which the tap is connected and I too believe there may then be two reflections but discrimination may be difficult.

TDRs can be and are used to locate intercepts (wire taps) on phone lines too.

Some bare TDR waveforms can be found here:
http://pe2bz.philpem.me.uk/Comm01/-%20TestEquip/-%20...

The fifth one shows a few small reflections caused by taps, followed by an unterminated end.

The ninth one shows a splitter in use (probably on coax), with reflections for the 2 legs.

In raw terms, I'd expect a TDR to be able to show reflections from every termination of a line.

However, while this ought to apply to bare lines, I don't know how they'd apply to a BT line that properly terminates in a master.

I imagine that a filter (such as an SSFP) does a good job of hiding any taps that occur behind it ... which should be fine. Taps behind filters are good. Taps before filters are the bad ones.

But 'seeing' it from an exchange based TDR is very unlikely, and still won't show if there is or isn't an SSFP on the NTE.

Just had a look at the availability checker again and is showing more things i don't understand

https://ibb.co/e6pBUa

Its showing something called VRI, NTEFaceplate and date last tested. Not to sure what VRI means, tried googling it but couldn't find much.

Voice Re-Injection

VRI ... pass ??

I do know they are increasingly asking for more data about lines we visit, what type, location, and is there an SSFP fitted.

I'm not to sure what SSFP means.

I'm on adsl2+ if that's what you mean by type. And my exchange is WSLON.

Edit. Had a google of SSFP, It came up with a bunch of faceplates. I use this one
https://www.run-it-direct.co.uk/images/VDSLMk4front.jpg

Edited by deleted (Sun 16-Jul-17 13:47:48)

SSFP Is service specific face plate.

Mine has N for all 3 and says it was last checked the day after yours. Not sure how they checked them as they certainly haven't been to the house or done any visible work on the line. If NTEFaceplate is whether there is a BT fitted NTE with built in filter then mine was installed by a BT engineer when installs were still always done by engineers (no self installs available).

Perhaps everyone's show as no until bt/openreach get the info they need? I'm not sure though.

Not had an openreach guy at my home in years so not sure how they got the info either. Did have a sky man over last year fitting a faceplate but that's it.