Exchange Only Line

OK. This one has me baffled. What precisely is the issue with an 'exchange only' line when the customer is C. 100ft from the exchange. I completely understand that an exchange only line is one that doesn't go via a cabinet and this might be an issue if the exchange was many miles away, but no one has ever explained (BT least of all) why a telephone line connected to the very epicentre of the local wired communications network a few feet away should be a problem when it comes to getting it hooked up to fibre. Surely, it's the easiest of all places to make such a connection?

No half baked answers, whinging arguments or plain guess work please. I need to be able to convey this to someone else. Just a clear and concise explaination why not being connected via a cabinet is a problem. No BT type, obfuscated answers suggesting I speak to Boris Johnson for political intervention or the Pope for spiritual intervention either. Is this a technological issue? (I do not believe this), Is this a kafkaesque regulatory one? (this I can believe) Or just plain lack of will by all parties concerned?

In reply to a post by Desmond:

What precisely is the issue with an 'exchange only' line when the customer is C. 100ft from the exchange.

Put simply the "fibre" services are delivered to you as Very high speed Digital Subscriber Line (VDSL) services. This requires a VDSL DSLAM at the other end of your phone line. For ADSL this DSLAM is in the exchange, for VDSL this DSLAM is in a second cabinet that is connected to the line at the first cabinet.

BT can't install a VDSL DSLAM inside the exchange for your line as this would put too much power onto the line and affect the other customers on older ADSL products (BT customers, TalkTalk customers and Sky customers, and any other LLU provider such as Zen).

All ISPs operate under an industry agreement (with Ofcom) called the Access Network Frequency Plan (ANFP) which is what limits this.

In some areas (with enough exchange only lines) BT openreach have basically cut the wires outside the exchange and installed a cabinet, often in the street close to the exchange. Then here they can fit a FTTC cabinet twin. Don't hold out your hope for this.

If you're that close, you should be able to get 20meg download and 2.5meg upload already on ADSL with Annex M ?

An excellent explanation James .

Nope! None of that makes sense. You failed at "too much power onto the line".

Feel free to try again!

In reply to a post by Desmond:

Nope! None of that makes sense. You failed at "too much power onto the line".

BT can't because of good technical and mathematically provable items that are complex to explain.

DSL is essentially a radio signal onto the wire. If you've ever done any amateur radio, or CB, then you'll know about transmitter power and antenna efficiency. If not, there are probably lots of good Wikipedia articles.

In reply to a post by jchamier:

BT can't install a VDSL DSLAM inside the exchange for your line as this would put too much power onto the line...

Also, there may not be enough space.

In reply to a post by RobertoS:

An excellent explanation James .

Thanks! Its still a very technical topic, and I'm nowhere near an expert. Just a constantly learning amateur.

Easest version: there is a rule saying they cannot do vdsl from inside exchange

So. What you are saying that if the line in question went 95ft to a cabinet outside the exchange you can get it connected to VDSL. However, if it goes another foot to inside the exchange it can't be connected to VDSL? Maybe this is becuae there is some strange Anti-VDSL field that exists on the other side of an exchange outside wall, but does not exist anywhere else in the universe? This field mysteriously causes huge amounts of 'power' to accumulate as your line passes throught the exchange wall that will affect other people, who are not connected to your telephone line at all.

I have a word for saying all that, but I can't use it.

Thank you Saffy. I was hoping you might answer. So, the simplest answer is that for regulatory reasons mere mortals need to be connected to a cabinet to get fibre. All this is because of chinese walls and kafkaesque regulation? Yes?

In reply to a post by MrSaffron:

Easest version: there is a rule saying they cannot do vdsl from inside exchange

Why not?

I'm less than 500m away from the Exchange, sure I don't expect Fibre, but why can't I get VDSL?

Surely VDSL is simply another interface, which could be located just as easily at the Exchange as it is in a Cabinet - the only real difference is that it must be a lot cheaper & quicker to provide!!

^{([cough] For someone asking for help, and given what as I said to the poster was a very good reply, that was extremely rude response from you )}

Anyway, have you ever looked at line stats from your router? If you haven't, we will need to go a little further. But if you have, you may have seen something like this-

Down            Up
SNR (dB):        6.1             6.7
Attn(dB):        19.5            0.0
Pwr(dBm):        13.5            7.3

Maybe you don't know what a DSLAM is.

Your router contains a single-line modem. A DSLAM is a rack full of "line cards". Your phone line is connected to one, and a modem on the line card is assigned to your line.

That power figure is what the DSLAM in the FTTC cabinet is supplying on my line.

There's a lot of other stuff feeding out of the exchange, like a few thousand phone lines and ADSLx such as you are currently on. That amount of power and the radio frequency emissions from a VDSL DSLAM situated in the exchange could screw up all those.

Even with non-EO lines, the power output on a line such as mine is carefully regulated to make sure that as it passes through the normal phone cabinet on its way to me it doesn't mess up any ADSLx lines running through that cabinet.

Does that help?

OK, I'm less than 500m away from an Exchange.

What is the fundamental difference, in the copper cable, between my Cable & someone else with 500m to a Cabinet?

They both go through the same range of multipairs & connections. If I was to get that level of interference, as you imply, so would the guy 500m away from a Cabinet!

Because radio noise from vdsl can clash with adsl2+ is the actual reason

The crosstalk from the two signals interfering

Hi John.

This bit of my reply to the OP possibly answers your question.

"Even with non-EO lines, the power output on a line such as mine is carefully regulated to make sure that as it passes through the normal phone cabinet on its way to me it doesn't mess up any ADSLx lines running through that cabinet".

I guess that level of control of the VDSL2 power within the exchange, plus the huge number of adjacent cables that have to be protected en masse from the VDSL2 kit and emissions/signals, would render the result at your end not worth the candle.

At the end of the day, as MrSaffron said, the regulations imposed on Openreach say no. Because of these factors and risks.

To fit the rule yes.

Vdsl is already held back to avoid interfering in the street

I do know that space was an issue at some exchanges in the past with ADSL. However, given they can fit a VDSL DSLAM for who knows how many lines into a cabinet on the street and the line is already connected to an ADSL DSLAM at the exchange and more and more people connected to the exchange are being connected to VDSL DSLAMS in cabinets on the street rather than ADSL DSLAMS at the exchange I somehow didn't think space was an issue.

Hypothetically, if I'm fed from a Cabinet 500m away, I would have a choice between ADSL & FTTC (aka VSDL)? But that same arrangement of Cabling, if fed to an Exchange, would create interference problems?

MrSaffron, I know you well enough to be confident that you are giving valid answers, but I really DON'T get it!

It is complicated and only understand as did rf electronics back in 80's

Reasonable precautions but rule is under negotiation suppossedly now lots ofreal world data

I'll try not to be rude, but this power thing and noise and the rest just sound like excuses. I suspect if the Queen was on an exchange only line at Buckingham Palace (rather than an outreach worker for homeless people living in an over priced ex-council flat on the other side of the river) they would all be solved instantly with a bit of metal shielding and some off the shelf kit that in the scheme of things costs tuppence a line.

It is clear this is not primarily a technical issue, but a regulatory one and that is all I (and the outreach worker) needed to know. She will thus almost certainly not be renewing the tenancy for her flat, but will move on to a location where she can get fibre, which contrary to her previous experience (and ironically) seems to be as far from the exchange as it is possible to get in London.

In reply to a post by Desmond:

I'll try not to be rude, but this power thing and noise and the rest just sound like excuses.

If you don't understand the technicalities yourself, you're on shaky ground belittling those who do.

In reply to a post by johnjburness:

but I really DON'T get it!

Most people who haven't done radio comms, won't get it sadly. Its complicated.

Have a look at this page, at the third document, ND1602, and download the PDF:
http://www.niccstandards.org.uk/publications/llu_spe...

You'll find its a 42 page document, and should tell you why. (Its not something I understand, and MrSaffron might be one of the few here who can explain the salient points, the summary in my first post is the high level !).

In reply to a post by Desmond:

It is clear this is not primarily a technical issue, but a regulatory one

Bit of both actually. Regulations to ensure technical DSL products work reliably. Which is why its run by NICC and not by a government quango such as Ofcom, or a company selling products such as Openreach or Kingston Communcations.

Excuses for what?

Why would Openreach, or the regulators, wilfully reduce the speed and coverage of rollout of the product nationally to what on the face of it to you and me should be the easiest customers?

BT, Sky and several other ISPs clearly don't understand the problems either if the exchange of emails I have read is to be believed. Hence my request for clear, concise answers that were in the realms of being believeable. I now have one.

"It is clear this is not primarily a technical issue, but a regulatory one"

Or maybe the regulations are due to technical issues ?

In reply to a post by Desmond:

Hence my request for clear, concise answers that were in the realms of being believeable. I now have one.

You had one in the first reply to your OP [shrug]

Stop making soluble technical excuses for problems created by badly thought through, politically motivated regulation.

The next thing you'll be saying is that looking at porn causes too much power on your line and that access to it needs to be regulated with filters and the like to stop exchanges accross the land from bursting into flames and thus denying orphaned kittens of food and decent cat litter.

Isn't that common knowledge?

Nope. That does not compute. If they were told the regulations required them to make this work or there was a compelling financial reason to make this work then they would make it work.

In reply to a post by Desmond:

Nope. That does not compute. If they were told the regulations required them to make this work or there was a compelling financial reason to make this work then they would make it work.

Yup, all they'd have to do is repudiate Maxwell's equations� piece of cake.

In reply to a post by Desmond:

if the Queen was on an exchange only line at Buckingham Palace (rather than an outreach worker for homeless people living in an over priced ex-council flat on the other side of the river) they would all be solved instantly with a bit of metal shielding and some off the shelf kit that in the scheme of things costs tuppence a line.

No, they would just build her her very own pair of cabs just outside the walls of Buck House (or even inside to preserve state secrets).

Feel free to explain why other countries have no problem installing VDSL kit inside their exchanges.

The past is a foreign country, they do things differently there.

A little check on one site for the line in question just now says "Fibre broadband is not available... take Broadband now and upgrade to fibre broadband when it's available." Dunno about you, but to me that suggests that it will be available in a reasonable time frame.

No suggestion there of the reality for the potential customer which is to all intents that there are no plans for it to become available anytime soon.

Am I completey alone in thinking fibre (or the potential for it) is being miss-sold to consumers?

In reply to a post by Desmond:

A little check on one site for the line in question just now says "Fibre broadband is not available... take Broadband now and upgrade to fibre broadband when it's available."

I'm sure Her Majesty will be able to get it expedited!

Talking about time, it's a little after 2.00pm in New Zealand (my sister has just reminded me with a photo of her in the garden). Apparently, apart from a sub tropical climate, in the Bay of Plenty, they also have anti-VDSL interference fields in their exchanges. Maybe we live in the wrong time zone or maybe anti interference technology in New Zealand is more than 13 hours ahead of us or maybe these strange anti-VDSL phenomena do not affect telephone exchanges in the antipodes.

Edited by Desmond (Sat 25-Jan-14 01:12:01)

We don't make the rules. The EU makes the rules and we just gold-plate them.

And gold is an excellent conductor .

That doesn't wash at all. Almost all the EU rules in this respect were modelled on UK privitisations and for the most part opposed by everyone else in the EU because they challenged longstanding national monopolies.

We couldn't have begged for a better deal were it not for the fact that we are woefully inadequate when it comes to exploiting such opportunities.

New Zealand has a population of 4.5 million and a 30GB download allowance on FTTC is £42.50pm.

Great .

All that may be true, but according to Bill this changes the laws of physics too. Can I therefore reasonably expect to find a Higgs Boson hiding in plain sight in Peru without building the equivalent of the LHC just outside Lima?

Edited by Desmond (Sat 25-Jan-14 01:53:49)

Why are you arguing with us when you know SFA? Go and argue your case with your MP and the regulators.

Or are you just trolling?

Higgs Bosons are all around you and in you, also would be in Peru.

Not the point either. The question was could you find one.

As long as it does not crystalise in to dendrites!

In reply to a post by jchamier:

In reply to a post by johnjburness:

but I really DON'T get it!

Most people who haven't done radio comms, won't get it sadly. Its complicated.

Have a look at this page, at the third document, ND1602, and download the PDF:
http://www.niccstandards.org.uk/publications/llu_spe...

You'll find its a 42 page document, and should tell you why. (Its not something I understand, and MrSaffron might be one of the few here who can explain the salient points, the summary in my first post is the high level !).

Have to be honest to say that I haven't studied the document completely, but it does give a useful diagram (Figure 1 � Application of the ANFP), on Pg 7.

This categorises circuits according to configuration. For an "EO" cct you are directed to "Part D" - which simply re-directs you back to "Part A" which covers full "metallic cables" (generally it means "copper") from Exchange to Consumer (albeit via a Cabinet) - in other words it is automatically assuming a relatively long line!

I really couldn't see any explanation why short EO Lines (with the Modem/DSLAM located in the Exchange) could not be treated in a similar fashion to Short Cabinet Lines (where the Modem/DSLAM is located in the Cabinet).

TBH, from this quote within the document ("It is for future study whether for these EO lines, an enhanced PSD Mask specification can be produced and agreed that would allow the use of higher frequencies than those allowed in Part A taking account that there is no SLCP for connection of transmission equipment"), it seems to me that EO VDSL hasn't yet been really considered!


Edited to add:-
ps:-
I have studied Radio Comms, etc, albeit many, many moons ago (hence not upto speed on latest technology). Obviously I understand things such as Cross-Talk, variable Propagation Delays, etc.

Edited by deleted (Sat 25-Jan-14 08:28:31)

In reply to a post by Desmond:

Feel free to explain why other countries have no problem installing VDSL kit inside their exchanges.

I realise that you're not in the habit of providing links so that others can verify your assertions and that the UK is invariably behind the rest of the world in its widespread provision of high speed broadband, but I'd like to see evidence of that.

The only ones I can find, whilst not explicitly denying what you say, imply that they are not doing so¹ but, unlike some on this bbs, I'm prepared to admit that I may be wrong. Provided that good evidence, not hearsay, is supplied.


¹ eg

In reference to point-topic.com/free-analysis/vdsl-broadband-in-superfast-europe/:

�Distance from the cabinet� reflects the fact that DSL performance falls off sharply with distance. Street cabinets in urban areas usually have all their users within a few hundred metres, which is fine. But there are always exceptions and, in rural areas particularly, individual properties, even whole villages, may be at the end of cables which are kilometres long.

The best way to address all these issues will be to build new networks, or network segments, to fill the gaps and bring distant users within VDSL range of a fibre point-of-presence. Such networks will require extending fibre, whether all the way to the home or reverting to copper for the last few metres.

- See more at: http://point-topic.com/free-analysis/vdsl-broadband-...

In reply to a post by johnjburness:

I really couldn't see any explanation why short EO Lines (with the Modem/DSLAM located in the Exchange) could not be treated in a similar fashion to Short Cabinet Lines (where the Modem/DSLAM is located in the Cabinet).

I think the point is that you can't look at VDSL in isolation- like it or not there's a lot of ADSL gear still around. VDSL equipment inside the exchange would be physically close to ADSL equipment serving other users.

Thus the (relatively) powerful outgoing VDSL signals would interfere with the (much weaker) incoming ADSL signals, some of which may be coming from very long lines, and degrade the performance of those lines to an unacceptable degree.

This doesn't apply to an FTTC cabinet which (obviously) doesn't contain any ADSL equipment, and probably wouldn't apply to a VDSL-only exchange if such a thing were ever built.

Does apply to cabinets but to less extent hence why three power masks are used based on distance from exchange.

In reply to a post by billford:

Thus the (relatively) powerful outgoing VDSL signals would interfere with the (much weaker) incoming ADSL signals, some of which may be coming from very long lines, and degrade the performance of those lines to an unacceptable degree.

That is a very good explanation of the potential problems that can beset a Cabinet, where it has a mix of locally generated VDSL signals, & "carried-through" ADSL signals!

So what is the difference at the Exchange end, though?

Have spoke anfp with various people and difference in uk is that a cautious approach is taken, a lets try and then fix it approach is more prevalent in some places. Hence some places rolling out before international ratification

In countries were adsl2+ takeup is less its less of an issue ie less rf in cable bundles. Also if just adsl probably easier. Some countries replace adsl with vdsl.

The presence of llu is a big uk difference ie talktalk sky and others have input into anfp

Originally believe aim was that short eo would be fttp but cost realities kicked in

Messy typing as on phone

In reply to a post by MrSaffron:

Originally believe aim was that short eo would be fttp but cost realities kicked in

I suspect that that provides a "hint" on the situation in as much that there was an assumption that short EO wouldn't be an issue as the "aim .... would be fttp"!

Certainly, the document, that jchamier linked to, states that "It is for future study" (which implies that EO VDSL hasn't been considered yet!)

well here's just a sample of the complexity relating to near and far-end cross-talk

http://www.princeton.edu/fastcopper/eusipco.pdf

I nave also perused ND1602; and generally agree with your comments - but there is a qualification in Part D, regarding EO lines-

"
D.1 Introduction
This part of the ANFP specifies the PSD Mask that applies to transmission equipment connected to the MDF at an MDF site when that MDF is connected to cables routed directly to the NTP (i.e. without being routed via a SLCP) and where those cables are not in a cable sheath with any metallic access cables routed via a SLCP.
"
Presuming that the implication is that these are the same (EO) cables-
"when that MDF is connected to cables ...... and where those cables...."

That does seem to imply a possible VDSL interference problem with any "Part A" sheathed cables, going to SLCP (PCP) Cabinets, where I understand there are HF Reject filters fitted to confine the FTTC-VDSL signals to the (very) final stretch from the SLCP/PCP in to the Customer's Premises.

That is, preventing the FTTC-VDSL signals leaking back to the Exchange MDF etc electrically, although probably this would be at extremely low levels given the likely Attenuation etc.

=======================

Another aspect that I wonder if it has any bearing on the matter.

Generally the SLCP/PCP cables will pass through the Exchange walls in relatively tidy groups; and at the SLCP/PCP, gives a nice, concentrated node "near" the various Customer Premises, that injecting the VDSL signals at such locations is relatively easy to do.

I suspect and would appreciate confirmation from someone with good Exchange Practice knowledge, that EO lines tend to pass in/out of the Exchanges at relatively widely scattered points, heading to/from the Jumpers and Risers etc (Or have the Jumpers and Risers gone?)

If the latter is the case, I suspect that to re-arrange them in to a tidy group so that a pseudo "FTTC SLCP/PCP" in the Exchange to provide VDSL to them, would involve quite a lot of extra work, tending to be almost unique in detail in each Exchange; and with a varying quantity of those pseudo cabinets, dependent on the quantities of EO lines and whether the specific EO lines are suitable.

Density of the cable bundles as they travel around the building, which increases the scope for crosstalk.

In reply to a post by eckiedoo:

Generally the SLCP/PCP cables will pass through the Exchange walls in relatively tidy groups; and at the SLCP/PCP, gives a nice, concentrated node "near" the various Customer Premises.

These bundles of E-side lines are indeed in tidy groups, of perhaps 1,000. You'll also find that they have a tendency to be pressurised (with air) as a way to keep moisture out, and as a way to indicate breakage.

There is some sort of manifold at the PCP-end of the line that provides the far-end seal.

E-side lines stay pretty much untouched. breaking into them for trivial matters is a no-no.

There's some posts here, including a photo of pressure gauges and a link to an Ofcom document that gives titbits about the access network (first post of second page).

Thanks for the fast reply, link etc.

You have confirmed that the SLCP/PCP cables pass through the Exchange walls in sealed, pressurised sheaths containing large numbers of pairs, what is the situation with the EO lines?

Do the EO lines range from single pairs "to the premises next door", to anything approaching being mini-versions of the SLCP/PCP cables above?

My feeling, from things I have read online, is that EO lines tend to leave the exchange in cable that is nearer to E-side in style, rather than D-side. That is, that it is still grouped quite strongly as it leaves the building. Perhaps more cables, each smaller than full E-side cables, but not individually.

[Note 1: The E-side cable I talk about can be made of separate cable lengths that are jointed. However, this is a one-time jointing operation, and the sheathing surrounding the set of joints is restored permanently to prevent water ingress. Perhaps, for old cables, in soldered lead sheaths.]

[Note 2: As I understand it, pressurised E-side cables tend to terminate in the ground (ie jointbox pits in the pathway), where they are jointed to short cables up into the PCP. There they are jointed, as needed, to a short linking pair that takes the connection back to a separate cable down underground to the D-side cables. The short linking pairs are the joints that are made/unmade when doing fault repairs, or routing through FTTC cabinets]

The main structural difference in the EO case is that the main EO-cable terminates underground, where it is jointed to more local D-side cables directly.

But I must add caution here - that is my interpretation of the way I understand it from the way I have seen things written written. It certainly doesn't come from absolute confirmation.

You might like another thread on the E-side and (in one of my favourite set of pictures) an american story under a flooded Verizon exchange

To be frank most of the retail arms of the providers have little to know clue about how xDSL and its many variants work and the nuances.

Each provider usually has a couple of people who do have a good idea, but they will be well hidden from consumer contact.

Suspect a lot of time on ANFP type issues has been around the whole vectoring concept.

In reply to a post by Desmond:

I'll try not to be rude, but this power thing and noise and the rest just sound like excuses. I suspect if the Queen was on an exchange only line at Buckingham Palace...

according to the bt checker, for the well publicised numbers and postcodes associated with the palaces (which i imagine are all direct lines to the exchange), Queenie doesn't have it so good.

Buckingham is on the whitehall exchange, with an EO line. which is currently "exploring solutions"

Balmoral Castle is on the crathie exchange, which is also an EO line. Ballater, just 7 miles down the road has FTTC HA!
Like most people on holiday, I guess she's a little cut off up there. And in London she's got to contend with the urban exchange problem, so there you go. Doesn't seem to be a money or privilege issue, I think it's just how the network is set up.

I suspect being on an EO line won't be an issue. There will most likely be leased lines serving the Royal properties.

Hi, sorry to resurrect this thread. I'm moving into business premises next door to a fibre-enabled exchange. Therefore EO only lines unfortunately. (Got Virgin thank god!)

Can I ask whether there is a minimum "safe distance" between the VDSL equipment and the existing ADSL equipment? Surely that's what is actually important.

According to what I've read, OpenReach could simply put a fibre cabinet on the opposite outside wall to where all the ADSL equipment is so interference would be a problem whereas they're not allowed to put it inside the exchange but at the opposite side of the building.

Have I understood this correctly?

Thanks

Nick

Edited by deleted (Fri 19-May-17 19:43:46)

Yep. The DSLAMS can't coexist in the same place basically.

I realise that but there must be a minimum separation required. If the exchange building is huge and there is space inside far away from the ADSL equipment then why can't VDSL be installed?

I've seen mention of 400m E side cable length mentioned. That would place the cabinet outside most small to medium sized exchange buildings . Openreach/BT also have a policy of trying not to place the cabinets inside the exchange grounds as this makes future closure more cost effective and less disruptive.

In reply to a post by nssimpson:

I realise that but there must be a minimum separation required. If the exchange building is huge and there is space inside far away from the ADSL equipment then why can't VDSL be installed?

I wonder also if its jumpering related ? The frames are congested enough already in some sites ?

In reply to a post by witchunt:

future closure

Sorry to disrupt the flow of the thread, but how does this work? Will every exchange be closed down eventually?

Edited by deleted (Sat 20-May-17 09:57:23)

I image the headend sites are pretty secure for sometime.

Eventually yes

PSTN turn off slated for 2025

So, is that prediction made on the presumption that everyone won't be served by an exchange, but by a different technology such as Gigaclear?

Edited by deleted (Sat 20-May-17 10:03:57)

Once everyone can be served by a fibre variant (FTTC/P) then only the head ends would be needed as this is where the fibres connect to. As a result of everyone being on some sort of fibre connectivity, then FVA/VoIP can be utilised which removes the need for all of the copper pstn kit in the exchanges.

Ahh ok, I thought so. So, basically only the exchanges that have the fibre in them will be kept open, whereas the smaller and only telephone exchanges will be closed?

Not strictly true as almost all exchanges have some fibre e.g. how WBC ADSl2+ and LLU ADSL2+ is linked back to core networks.

Only exchanges that are GEA Handover nodes are likely to remain, and even then you can reduce size to just a few 19" rack style cabinets

Probably, but as they occupy less space in each building, the leaseholder may look to not renew leases to find a better return

In reply to a post by MrSaffron:

Probably, but as they occupy less space in each building, the leaseholder may look to not renew leases to find a better return

Which brings us right back to the irreversible but lunatic decision taken many years ago by BT.

My wife spent all her working life in first the GPO, then BT when the split with the postal service took place. Two major changes happened to her work in the properties division in respect of exchange building.

First was the change from acquiring expansion space to cater for growth, preferably immediately adjacent to existing exchanges. That changed very rapidly once the new much smaller equipment became available, so she started selling instead. Nothing strange about that, but remarkable in the way a job and how all jobs in all businesses are about to.

But the point you just made about the leaseholder shows the daft change. The principle when buying exchange buildings was that they had to be purchased freehold, not leasehold. (Ground rents being a different matter). There was a complete policy change at some point. All retained buildings had to be sold and leased back.

Good for the balance sheet and shareholder dividends, long-term as stupid as building hospitals under Public Private Partnerships.

The chickens on both are currently coming home to roost. As they will during the life of Hinckley Point and more so at the end of the fixed price period.

Sorry to bring non-exchange issues into the thread, it was to demonstrate how the leaseholders leaseholding of exchanges came about and how stupid it is in the long term.
_{^{Edit: Typo "leaseholders" correction.}}

Edited by RobertoS (Sat 20-May-17 15:53:13)

That was the brainwave of Ben the clog.

I think it pre dated Ben. Peter bonfire?

Makes sense, thanks.

In reply to a post by RobertoS:

In reply to a post by MrSaffron:

Probably, but as they occupy less space in each building, the leaseholder may look to not renew leases to find a better return

Which brings us right back to the irreversible but lunatic decision taken many years ago by BT.

I thought I read somewhere that, eventually, BT Group plc purchased the company that owned all the buildings that the Group businesses occupied.

Does that ring any bells?

Maybe a rump holding was sold to a single company, but the sales and leasebacks my wife was making were individual transactions with whoever wanted to play.

To sell the lot to a single company would have been almost impossible. BT was at peak one of, if not the one, biggest property owner in the country. (Not land, IIRC that was the MoD, and not by total retail value - hasn't that been the Duke of Westminster for decades?)

As for buying them back, with property and land values having risen dramatically that sounds even less likely. We come back to MrSaffron's original post re the leaseholder perhaps wanting a big rent increase. I am sure we did see an actual case not long ago where a small exchange was closed for just this reason. The commercial value of the land was huge and the leaseholder wanted to realise that value.

Edited by RobertoS (Sun 21-May-17 09:49:29)

That would be Chelsea where all cabinets now offer VDSL2 and no EO exists anymore.

I think they brought the facilities management back in house

In reply to a post by witchunt:

I think it pre dated Ben. Peter bonfire?

Under Peter Bonfield BT posted the biggest financial loss in British corporate history (up to that time) but he still walked away with £13M .Selling off all but 2 BT buildings was Bens way to clear the debt , at the time all the money BT made was not even paying off the interest .

Thanks .

I thought that there was an European Directive requiring electrical/electronic equipment not to cause interference and similarly not to be affected by any interference that may be picked up? Or words to that effect. CE marking requirement perhaps?

Amazed!

Indeed.

DSL MSANS and DSLAM's do not cause electrical interference from their power supplies


It's the very nature of the technologies used and the frequencies utilised that makes them for the moment, not compatible.

So what about two customers on the same cabinet and same cable back to the exchange, where one is on ADSL and the other on VDSL? (And I guess, their variants)

Seems strange.

Cheers!

It's the same reason why ADSL can't be provided from the cabinets. Would solve a lot of speed issues for customers.

Don't you think that would have already been done if it were possible?

There are filters in the cabinet that prevent any cross frequencies. This is one reason why the LR-VDSL technology is undergoing much testing and discussion, as it requires ADSL to not be present on any line from the cabinet.

If you think it so easy, I'm sure Openreach would be delighted to offer you a job.

Edited by deleted (Sun 21-May-17 21:25:32)

No, I don't think its easy at all. I spent 20 years wondering why someone (ITU maybe) had allocated the same 12 MHz band HF frequency the Post Office for radiotelephone ship communications as they had allocated to Norddeich Radio in Germany. 12 MHz being a good frequency for comms of the west coast of Central America....

I got my cable wrong in my previous post.

I am about 500 metres (as the cable goes) from the FTTC which serves me. Same cable, same wooden pole, the person across the road has ADSL.

I would have thought (dangerous, I know) that the cross talk in that 500 metres would be as bad as a FTTC on the "wrong" side of the exchange wall.

Cheers!

The crosstalk isn't "leaked" in the pairs as there is a small gap between the upper ADSL frequencies and the lower VDSL frequencies.

The issue is with the higher power output from the VDSL kit can interfere with the ADSL kit in the exchange, breaching the ANFP.

Here's some light reading http://www.niccstandards.org.uk/files/current/nd1602...

Edited by deleted (Sun 21-May-17 21:55:29)

In reply to a post by Ancient_Mariner:

So what about two customers on the same cabinet and same cable back to the exchange, where one is on ADSL and the other on VDSL?

They aren't. At least, not in the way I read your post.

The PCP <> exchange copper down which the ADSLx travels doesn't change when someone goes on to FTTC. Have a read of this well out of date page. The connections and traffic movements are correct though.

Frequently these days the optical fibre doesn't even go to the phone exchange, it goes to a bigger one in the area which has the Openreach kit to hand over the FTTC to ISPs. VDSL2 only exists between the FTTC cabinet and the end user.

The FTTC cabinet contains a DSLAM, as in olden days the exchanges had. (I expect some still do, but MSANs are the latest stuff with more capability). The DSLAM merges digital traffic from the fibre exchange with the analogue phone signal giving an analogue output with phone and VDSL2 frequencies present. Splits them on the way back from the user.

I went back and looked at the early part of the thread. It is pretty laughable.

The reason we don't get VDSL DSLAMs in the exchange is indeed crosstalk. And there are all manner of RF electrical engineering reasons why crosstalk is a threat to DSL.

However, the reason that this crosstalk is a threat in Britain but not NZ is, well, typically British...

In reply to a post by lee111s:

Here's some light reading http://www.niccstandards.org.uk/files/current/nd1602...

The ANFP tells you what is and isn't allowed. But it doesn't really go into details *why*.

There's a newer report out of NICC as a result of a study whether VDSL2 could ever be allowed from the exchange:
ND1517: Report on the Technical Feasibility of Deployment Options for VDSL from the Exchange

That document makes it clear that, if EO lines were really pure EO lines, then VDSL2 would be feasible.

The problem is that EO lines aren't really pure - they can share the E-side and/or D-side with cabinet-based lines - and that such shared wiring isn't well documented. Even worse, EO lines have been patched into cabinet-based D-sides in small segments, as part of fault-fixing.

It also seems that the biggest risk appears to be to upstream signals, especially as UPBO is in use.

Thank you for that detail. With Mrs S having being involved, the accuracy cannot be disputed.

In reply to a post by witchunt:

I think they brought the facilities management back in house

BT Property Services, BT Property Management or some such-like named entity, I will presume.

When did our esteemed staff member/Editor decide on a gender re-assignation?

Heh!

BTFS - BT facility services

In reply to a post by RobertoS:

The FTTC cabinet contains a DSLAM, . . .

To be absolutely correct, the Huawei SmartAX MA5616, the SmartAX MA5603T and the ECI Hi-FOCuS MiniShelf M41 are all MSANs . . . which are just used as DSLAMs.

In reply to a post by RobertoS:

When did our esteemed staff member/Editor decide on a gender re-assignation?

I wondered if anyone would question that! But knowing the significance of your prefix S, I don't think I need to type any more.

In reply to a post by lee111s:

BTFS - BT facility services

Thank you.

Ah! We live and learn.

In reply to a post by burakkucat:

... But knowing the significance of your prefix S, I don't think I need to type any more.

?
Pass.

Meaning what ? Do you mean the suffix on my nick, which is the initial of my surname, or something else?

In reply to a post by RobertoS:

Do you mean the suffix on my nick, which is the initial of my surname, . . .

Yes and yes, I am aware of your surname.

Not a lot of secret about it LOL. Though I could hide it these days.

It's happened at the Hastings exchange. About 10 years ago the equipment was moved into an annex at the back of the exchange building and the rest was sold off. I was driving through Tunbridge Wells last month on my way back from visiting my sister and notice the exchange building on St.John's Road is being converted into apartments.