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BT Wholesale’s UK Broadband Checker Adds Status for Bridge Taps

Tuesday, May 16th, 2017 (8:08 am) - Score 8,473
bt_wholesale_bridge_taps_broadband_line_checker

The BT Wholesale Broadband Checker has recently added a new row to its output that appears to very generally reflect the status of a wiring issue known as a ‘Bridge Tap‘, which so far as we can tell only shows when testing with a specific telephone number (not address or postcode checks).

The term Bridge Tap was previously only alluded to in the checker’s description (below the results output), where a piece of text states: “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.”

A Bridge Tap is a physical issue with the copper line that can occur when an unterminated wire is not dealt with correctly (e.g. left connected to your circuit), which may result in your broadband service suffering more disruption due to interference and a higher volume of errors (i.e. your speeds will probably drop). Such problems aren’t a big deal on the voice side but they’re bad for broadband.

In simple terms it’s a bit like turning the wire into an antenna that catches noise and that’s bad for copper line based ADSL, FTTC (VDSL2) and G.fast services. We’d expect the status output options for this new row to be ‘Y’ for Yes, ‘N’ for No and the ‘U’ is probably Unknown. Most people are likely to see a result of N or U.

Some Bridge Tap problems are easier to solve than others and an engineer is often required. Switching your service to a new pair is likely to be easier than removing the bridge tap itself, depending upon where the problem is located.

bt_wholesale_bridge_taps_broadband_line_checker

Thanks to Peter and Chris for pointing out the change.

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Mark Jackson
By Mark Jackson
Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on Twitter, , Facebook and Linkedin.
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7 Responses
  1. http://www.dslchecker.bt.com/adsl/adslchecker.welcome if you can’t view the link in the article due to SSL issues with the BT checker.

    • Bit annoying that they still haven’t fixed that. The problem has been present for awhile now. I’ve changed the website URL to a direct one that cuts out the iframe.

  2. Avatar Steve Jones

    Bridge taps can be an issue in home wiring too. When I did a test and connected the VDSL modem/router to the master socket (not the test socket), then the roughly seven metres or so of balanced pair left to my study socket reduced the sync speed by about 45%. The general rule, is make sure that the only unfiltered phone pairs in your house is one that ends at your modem socket. There should be no unfiltered pairs T’d off or running beyond the modem socket. Sticking filters in the sockets doesn’t do the same thing nor leaving sockets unused. Odd as it might seem, a daisy chain with the modem one at the end works fine as long as their are micro-filters on any sockets which are in use.

    The impact of bridge taps isn’t quite like that of something like the bell-wire, as the extra tap is balanced. The problem is that signals reflect off the un-terminated end of the T connection and partially cancel out the signal in rather complex ways. Theoretically if the end of the unused T were to be terminated with a resistor equal to the characteristic impedance of phone wire (nominally around 600 ohms, but it’s not very well controlled) then it ought to reduce the effect.

  3. Avatar Marcus

    Worth noting the actual checker page will now work from the link in the article (at least in Chrome) as the frame / page for the actual checker uses a SSL certificate signed with SHA1 algorithm, which Chrome and others will identify as an insecure weak algorithm.

    You can either use the non https url of: http://www.dslchecker.bt.com/ or accept the certificate error if you visit the checker directly. https://www.dslchecker.bt.com/

    ERR_CERT_WEAK_SIGNATURE_ALGORITHM

  4. Avatar MrIcaras

    Bridge taps are internal. There would never be a reason for a bridge tap to be in the Openreach network.

  5. Avatar Chris P

    so if the checker shows WBC FTTP Availability Date as available with fttp on demand in the left hand column. Does that mean ISP’s can sell me FTTP or do i have to do something else?

    Only 5 houses on my road are serviced from this pole and cab is ~1.1 km away, the rest (60 odd) are serviced from a cab ~200 meters away but only has adsl, due for an FTTC upgrade in October, the other addresses do not have fttp or fttc listed on the dsl checker. Effectively my neighbours neighbour ~20 meters away from me on the same side of the road, does not have fttc or fttp as an option but i do, which is why i’m wondering if i should be able to order FTTP, if its only the expensive on demand option why do the other neighbours not also have that as an option?

    • Avatar MikeW

      You can order an “FTTP on demand” product, but not an “FTTP” product. There’s a very limited set of ISPs willing to take the order, but expect a minimum of 3 years at £300pm, plus installation greater than £1,000.

      BT’s (old) specification for where FTTP-on-demand would become available was: everywhere that has FTTC, including places on an FTTC-upgraded cab but too far for VDSL2 to work. Which probably explains why the other neighbours don’t get the offer.

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