Bridge-tap on my line

[#1]

I've had all excuses so far, from it's your wifi(my favourite), to we are not allowed to show you the results of a kbd test, to we aren't sure whether we are allowed to show you that.. my god

So a case was opened with BT to review why I have a bridge-tap on my personal line, and good old BT fashion they tell you nothing, but should have updated PlusNet with the issue. What I received was your line has been stable for 48 hrs, we will now look to close the case. Well that is very enlightening thank you, seen as those the last conversation I had they said to wait 72 hrs before getting back to PlusNet. Now they are closing the case..

Can you not do that, and please find someone capable of providing a non selective kbd with test results that include details of a bridge-tap.

[#2]

Here you go:-

Interesting that an availability check here suggests that the bridge tap condition was not being detected back on the 12th.

That said, your connection remains stable, you are synchronising at headline speeds, and there are few errors reported on the line.

There's nothing to say this is the case, but it's worth north noting that a bridge tap can be detected as the result of issues with your internal wiring/cabling. 

[#3]

Cheers Bob I appreciate the efforts. And thanks for providing the results in full. I'm disappointed that the Bridge tap remains after being told yesterday that it didn't, and even receiving partial kbd details to back this up.

To clarify, I currently have the modem connected to the main socket which is a complete inconvenience as a 12m cat5e cable then needs to trail to my computer until this is resolved.

Now forgive me if I'm wrong but aren't bridge taps a sign of bad cabling? Spurious unterminated wires left connected to the circuit causing interference? This requires an engineer to attend the cabinet I order to resolve I would have thought. If I need to pay, to improve my service I would happily do so.

[#4]

It depends.

Those 'unterminated wires' can be artifacts of your internal wiring too.

If you have the modem connected directly to the master socket, and nothing else connected to any extension socket anywhere else in the house (assuming there are any), then you've probably nothing to worry about. If you're using a filter, then it might be worth swapping that out too.

What exactly is the issue anyway? I can see there was a bout of instability a couple of days ago, but prior to that you'd had an uninterrupted PPP session spanning almost a month.

Given that things have been stable for approaching 2 days again, then it might be worthwhile seeing how things pan out.

[#5]

I only use one socket, and as I've already specified it it the master socket for the household. I do not use a landline phone, so no other sockets within the household are used. There is no other cables used. I game a lot, and play for frame. My response times are 40ms, and I also suffer from packet-loss, constantly seeing loss from game stats.

What I would like to know is what have BT done to correct this issue? Have they even looked at the cabinet? What has actually been done, except for waiting for me to go away?

[#6]

Something worth clarifying, you say "no other sockets withing the household are used" and "no other cables used".  Do you mean that there are other sockets and cables, but you just don't use them, or are there no other cables or sockets connected to your phone line?

Also when you say you are connected to the master socket, is that the test socket behind the faceplate or just into the front of it?

[#7]

Nothing connected to any other sockets. Only socket with something connected is the main for the modem only, and that has been the case since the case was opened.

[#8]

Ok, just reread what you asked.

The modem connects to the main socket. Running a kdb test would not pickup issues with a cable beyond that. Cable between the router/modem to peer is tested.

[#9]

Possibly showing my ignorance here but many decades ago I had a teacher whose mantra was: "Never be ashamed to show your ignorance but be ashamed to remain ignorant".

As I understand it a bridge tap is an unterminated cable connected to the loop between the exchange and the router. I do not see how this would be any different if the unterminated extra cable was linked in on a pole outside a house, possibly a left over from the days of party lines, or actually connected at the master socket upstream of the filter. If this is the case then any house internal wiring connected to a standard single socket faceplate is in fact introducing a bridge tap. For this reason it is desirable to fit a filtered faceplate so that any internal wiring is on the filtered phone side and therefore isolated at DSL frequencies. Can some-one please explain if I understand this correctly.

As an aside I recently sorted out a friends internal wiring. Initially there was one extension to another room from a single socket Master faceplate. There were 'dangly' filters (possibly old ADSL ones) fitted at both the master socket and extension. The line was synchronising at approximately 5Mbps. After removing the faceplate and just using one dangly filter in the test socket the sync rate went up to 15 Mbps. I then replaced the faceplate with a filtered version, dumped the dangly filters and reinstated the extension, the speed increased to 18Mbps. Presumably the DLM then got to work and the last time I checked it was running at 22Mbps and 3.2dB SNR. This has certainly brought home to me the significance of internal wiring and the need for decent filters.

[#10]

This is what the test socket is for. Accessing the test socket should disconnect any other extension sockets, if that removes the bridged tap, then the bridged tap is due to your extension sockets.

Yes the kbd test would detect any unfiltered extension wiring connected to the line.

[#11]

If it wasn't for the fact I'm currently using the master socket, i would consider your input and anything else to try move this forward.. . I did actually research changing the master socket in the house and will likely do it anyway once the bridge-tap/loop is diagniosed.

I use only one socket, this socket is a white socket, and is labelled BT. Only this socket connects connects to the modem, no other sockets are, and no other sockets are in use or have adsl filters attached. The home was built in 2007, the standards of cable I would only assume degrade as minimal.

[#12]

Thank you ejs.. the master socket being the test socket which rules out any internal wiring.

I await PN to arrange engineer to attend cabinet.. hopefully this year seen as though I have been trying to achieve this since joining almost 2 years ago!

[#13]

Does the master socket have separate sockets for phone and modem, or does it just have the single phone socket?

Plugging the modem into the master socket does not negate the effects of unfiltered extension sockets. It does not matter that there is nothing at all plugged into any of the extension sockets. The standard of cable used makes no difference, it is how the wiring is connected that can make it a bridged tap.

If the extension sockets are daisy-chained, then if you plugged the modem into the last extension socket, then the extension wiring wouldn't be acting as a bridged tap.

[#14]

Posts crossed, I suppose you could check all extension sockets are dead when connected to the test socket, if not then they aren't wired properly.

[#15]

This is a single socket. There are no other devices connected.