BT SFI Should not exist any more

It is a while since I have ranted about "Special Faults Investigation" service that Openreach sell.

Why did SFI exist?

• Openreach sold a service called metallic path or shared metallic path which is the wires from exchange to master socket. The standard for it was that of wires capable of making a telephone call, though the standard was improved in time.
• BT Wholesale (at the time pretending not to be the same legal entity as Openreach) buy that, add equipment at the exchange (DSLAMs), backhaul, more equipment (BRASs, switches, etc), more backhaul, and sold a DATA service, at one end being a hand over (typically at a data centre) which is fibre with ATM or Ethernet, and at the other end the master socket with ADSL encoding.
• ISPs buy that and add equipment in the data centre (LNS, Switches, DNS, email, etc) and transit and peering links, and sell an INTERNET service to customers - sometimes terminating at the master socket as ADSL, sometimes including a supplied router and Ethernet and/or WiFi

This system worked pretty well, and at each level someone is providing a service to some spec for a fee, and if the service breaks and does not meet that spec, then of course, they have to fix it, at no charge to their customer. Each layer builds on many parts to make a service to their customer.

This is where SFI comes in - there is gap. If the metallic path breaks, Openreach will fix it, however if it meets the spec (based on telephone calls) but is not good enough for ADSL data (e.g. below the min sync level BTW have agreed with the ISP), then Openreach DON'T HAVE TO FIX IT because it meets the metallic path spec. So they SELL an extra service to BTW, a Special faults Investigation, which, for a fee, involves the engineer trying to improve the metallic path (beyond the spec) to be better for data (e.g. ADSL). BTW have to buy this so as to fix the broken data service that they are selling to the ISP.

Why was SFI controversial?

All of the above sounds fine, at first. Bear in mind, BTW sell a data service to ISPs, and if a DSLAM breaks they will get it fixed (at not charge to ISP) and the same should apply if the data over the metallic path breaks (e.g. below agreed minimum sync rate), and again as not to spec that should be at no charge to ISP. But BTW DID CHARGE ISPs for the SFI. What is worse is many ISPs then charged their customers for the SFI!

This led to a lot of disputes, and the pettiness got mental. Some examples are BTW used to say SFI was optional so on all faults said we do not opt for SFI. They then refused to actually fix lines unless and SFI was booked but said charge was for work beyond the master socket, so we said do no work beyond master socket. They then said they could not accept that request, and also said that a visual inspection of the end user router and wiring counted as (chargeable) work beyond the master socket. At one point we instructed customers (who did this) to remove their router and all wiring and physically hide it out of sight before the BT engineer arrived. We had pictures even. BTW still tried to charge. On one occasion the engineer immediately closed the fault as "no customer router plugged in", without testing or fixing the fault! We have done well disputing SFI charges at every stage, usually quoting their own terms to them and again explaining that we (as an ISP) are not buying a metallic path.

Note: there is a logic for a charge for wasting time - reporting something that is not a fault, e.g. an engineers visits and finds the end users router is on fire - a charge on that basis, as a penalty of some sort, does make sense and makes sense to be passed on to whoever screwed up.

Why should SFI not exist now?

Now we have the crux here - we are still getting SFI charges, and still spending time disputing them, but for almost all lines SFI should not exist. To explain, that initial bullet point has changed for most lines now - because of the UK telephone service switch over from old copper pairs to the exchange.

• Openreach sell a DATA service with handover on a fibre at the exchange, Openreach equipment in the street cabinet, and wires or fibre to the end user premises handed over as VDSL or Ethernet.
• BTW buy that DATA service, and have equipment at the exchange, backhaul, etc..
• Etc

What we have here is no longer a gap - no longer is Openreach selling a metallic path and BTW using it to sell a data service. If the data service is not working it is Openreach not providing something to spec, and so Openreach should fix that as a NORMAL FAULT INVESTIGATION. There is no gap for which SFI was invented to cover. Indeed, BTW should dispute every such SFI charge before even thinking of charging us (ISP).

There are still some ADSL, but they are quickly going, so SFI could exist for those lines for now - with the same original controversy of BTW trying to charge ISPs, but this is dwindling. Somehow BT try to charge for SFI for VDSL and FTTP services even now where it logically makes zero sense.

If BTW really are separate from Openreach now, they really have no excuse for not disputing every SFI charge related to FTTC or FTTP on this basis.

Giving BT some credit where it is due

One thing BT never had the nerve to do with all their changes to contract terms was make it so that their customer would have to pay them to fix a service they agreed to provide, but were failing to do so. Such a contract, even on a commercial basis, would be very challenging, and I would hope OFCOM could be persuaded to step in if that happened. The basic concept of I agree to pay you for a service and you agree to provide that service relies on the provider having to provide what they agreed, or they fix at their own cost. They tried a lot - the whole visual inspection is perhaps the most creative, but never that.

I may not be able to say that for all providers, but that is another story.

Wallet inspector

What is fun with a nice UV ink jet printer is on what you can print...

One thing is a bank card.

This is now my Monzo card, oops.

Yeh, I can print on a card and the new non-embossed cards are even easier.

Someone suggested I make a flashy web site offering this as a service just to see how many people will send me their bank cards to print. It really is the 2026 version of "wallet inspector"!

Elegoo Jupiter 2 3D resin printer

I decided to upgrade my Elegoo Saturn Ultra 16K to an Elegoo Jupiter 2. So this is how it is going...

Resin printer basics

For those that do not know, a resin printer has a tray of goo (resin) in the base, under which is an LCD. The bottom of the tray is a "release film". There is a flat plate suspended above, it lowers in to the tray, a layer of resin is cured, and it lifts off the release film, and then down again for next layer. Eventually the final print hangs from the base plate. There is some messy cleaning and extra curing then to make the final part.

The Saturn had some challenges

I am sure I have griped on this before, but the Saturn had some issues...

The cover was a big top, sides, and front that hinged at the back top. To lift it up you would obviously grab the top sides and push up. The problem is that this motion would easily tip the whole machine back. The trick is grab the bottom sides and pull towards you and then up.

Then the print bed is clamped in placed by a small lever that you push up to release. It is small and stiff, and you push up with palm of your hand. And, you guessed it, this motion would tip the whole machine back. The trick is hold the top back of the machine with one hand while you do this so it does not tip.

However, the print bed is pushed forward when you do this - I never had this happen, but there is a risk it comes off the mount and crashes in to the tray of goo and LCD and smashes it all in a very messy way. So the trick is hold top of machine with left hand, push left elbow to front of print bed, and then lift level with right hand, and hope you do not get covered in resin.

Why does tipping the machine matter? Well, because you have a tray full of goo and if you tip the machine it pours out of the tray in to the machine. This is bad in many ways, not least of which is the machine then leaks goo from the seams for weeks. But also, at the back, directly behind the tray, is the z-axis motor and screw thread, with a big hole around it - so the goo goes right down in to the z-axis motor. This basically burgers that motor. I managed to get working fairly well with a lot of alcohol, lubricant, and running bed up and down for hours. Still not 100% but good enough to be printing again. It needs replacing.

Obviously you have to top up the tray to a level to cover what you are printing, and that makes spills even more easy to happen and more messy when they do.

Finally, changing the release film is a LOT of screws/bolts and very fiddly. Thankfully I realised I rarely need to change if, after a failed print, I use the cleaning cycle which exposes a whole layer you can peel off with any remaining print debris. However, on one occasions it got pierced somehow and I then had to change the LCD screen protector as well as it had resin sealed on to it. Resin printers can be messy.

Also, the print area is not very big, but more than big enough for what I normally print.

Apart from that it is good, and prints well.

An interesting feature is the tray and LCD tip down at the front as part of the release cycle, neatly peeling off the release film from the latest printed layer. Very clever.

The Jupiter

This is different and a bigger machine.

It has a bigger print area, nice.

It has side opening doors, solving the tip back issue.

It has a very long level for release of the bed, which can simply be lifted between thumb and forefinger with no real effort, or risk of tipping the machine.

The z-axis seems to have a cowling to protect from spills.

Even the release film change is a module with a frame and film that simply unclips and a new one clips in place. Costs more, but a lot less effort.

It even has tubing and an auto fill of tray from a bottle at the back, meaning it keeps a low level in the tray - way harder to spill and way less messy when taking off print bed. It can suck that up back in to the bottle for you as well.

I mean that was almost every single gripe I had sorted, well done.

The downside

Sadly there are problems.

It sucks!

That is the main issue. Unlike the Jupiter the print tray and screen do not tilt down to peel off the film from the print, instead the print head just pulls up after the printed layer. It often strains and snaps up. This clearly sucks on the release film, a lot.

After a few small prints I now have creases in the release film which mess up the print.

What is worse is Elegoo's response.

In summary (a) tough, and (b) my fault somehow. I am using all the default settings the app picks knowing printer and resin, and only printing a few small things with which the Saturn had no issues - even so, saying "yes it has a large print area but you can't actually use it" is mental. Where are trading standards when you need them?

Taxing home internet

There seems to be a proposal to change TV licensing to a tax on home internet! Thanks to this article from ISP review.

I hope it goes nowhere, otherwise I can see myself being an expert witness to parliament, again!

The proposal is "that every home with a broadband connection could automatically help to fund the BBC, even if nobody in the house watches live TV, via a new £11 (monthly) “Home Internet Levy” on their existing ISP bill".

As someone that runs an ISP this immediately rings alarm bells. So let's look at how this could possibly work.

To be clear: I am not covering the merits of the BBC - there is much one could discuss on such things - let's assume the BBC continuing is sensible - let's look at this proposal on that basis.

What they imagine?

My guess is that those proposing this assume that the vast majority of households have a single internet service from a big company ISP, so getting the ISP to add an £11 levy to the bill is simple.

The reality...

The reality is different. There are hundreds of ISPs, large and small, some very small (think a dozen people on a WiFi in a village). The admin is not going to be simple. But there are also a lot of edge cases, and these need to be addressed - even a small minority impacted by, say, paying twice, would cause some uproar.

Multiple lines

Some households have more than one internet service. It could be multiple lines from one ISP, which is not too hard to address at the ISP level. But as an ISP we have no idea if someone has internet at their house from another ISP. If we are to avoid double billing such people (and I really think we should, after all we never double billed people with two TVs) we need a way to sort this. So does a customer tell one ISP they have service from another, send a copy of the bill - that is not difficult to forge, but also impossible for the ISP to validate. Maybe we need a national database of which ISP is the tax collector for each property - that won't be simple.

Business lines

Another small snag is business services. At present a business premises may need a TV licence if they have a TV, but most business premises do not have a TV or need a TV licence, so we need to exclude businesses from this new levy. After all it says home with a broadband connection.

So do we exclude business premises - well this is more admin, and there are databases which identify a premises as commercial. But remember, a lot of people work from home. Indeed, a business service from an employer in addition to a home internet at the same house is one reason you may have two internet services at a house. Mind you, my house, an ex pub, is listed as pub/nightclub on BT's database still, yay, no £11/month for me.

So maybe exclude a business service? Is this down to how the ISP sells it? We sell home and office (business) services. The business ones cost more, but not £11 more - so all our home customers would be mad not to switch to a business service and save money - we'd love that as we charge more for a business service but would not have to send any of it to the BBC.

OK, what if only services sold to a business? Again, people work from home, and there are sole trader businesses. If one can save £11/month by putting down a business name, everyone will.

OK, what if only to limited companies? You know a lot of solicitors offices are a partnership not a limited company - they will love their internet service having an £11/month tax. Of course, it would also be easy to order home internet, and pay for it, but put in the name of a random limited company - hard for ISP to police as companies do this - ordering internet for an employee at home. As long as paid for, not an issue - but when not paid for then the ISP is chasing a random company that has no clue. Putting that fraud encouragement aside, it is less than £11/month to create a limited company and the annual filing!

Shared service

This sort of comes down to small ISPs, but what of blocks of flats with a fibre, paid for by the community or housing association. One £11/month fee? Or does the HA have to collect the tax per home?

There are a lot of WISPs (Wireless ISPs) that do this on such a small scale as well.

Mobile service

This is another huge issue. Mobile internet access would not be included, well we assume not. If it was, you have households paying not just twice, but three or four times over because multiple people have mobile phones.

However, a mobile based home internet is a thing - a 5G router with a SIM and WiFi access points. This is a viable home internet service already - usually in cases of good mobile coverage and poor internet "lines", i.e. where feeding a new fibre is hard. It competes with traditional landline / fibre services already. If mobile services are excluded, that changes the economy here. It will cause people to prefer mobile home internet as cheaper. It skews the market which can impact businesses and infrastructure as well.

Of course, someone will say there are ways to differentiate a 5G router and a mobile service - but how? There are mobile phones and iPads that never leave the house, so not by location. And you can usually put a normal mobile SIM card in a suitable router/WiFi without mentioning it to the mobile company. Even if you cannot, just get an old mobile and suitable SIM in hotspot mode as your cheap home internet.

Auditing ISPs

Another issue is that there are a lot of ISPs, and you won't even know of them all with ease, how do you audit that they are (a) charging all home customers £11/month, and (b) if they are, that they are passing on the full amount? Who is going to do these audits, and who is going to pay for them?

Existing special cases

Of course, TV licensing has special cases for blind people and old people. Scrapping these exceptions in any new scheme would also cause uproar. How the hell can ISPs check these things?

One reason this is all silly

The whole TV licensing thing is odd anyway, it was a Wireless Telegraphy Act thing, a licence to operate radio receiving equipment. That alone is odd, licensing transmission equipment sort of makes sense because of limited spectrum and risk of interference, but no reason to licence receiving equipment (apart from a money making scheme, oh, that's the point).

This got expanded to cover ways to get TV over wires (cable TV, etc), which itself made the whole Wireless Telegraphy thing even dafter. It has moved to, I think a Broadcasting act, and I think now Communications Act, not sure.

Now, remember, whilst this started small, radio equipment licence, it quickly became an All homes in the UK fee - basically everyone had a TV (almost) so everyone had to pay a TV licence.

At that point it would have made sense to move BBC funding to being from general taxation. But that did not happen. Instead, as usage of TV changed the rules have got more and more convoluted over time.

The objective is to try and make it All homes in the UK again, clearly. The idea of taxing home internet is clearly based on the ideal that everyone has home internet.

But why do that - why make it a convoluted tax, which needs huge admin, and a lot of exceptions and special cases which make for loopholes. We have per home taxes already, if they went up by £11/month but no TV licence, a lot of people would be happy as paying slightly less.

This would be a hell of a lot less hassle, and for a lot of people less money and one more thing not to worry about. No more criminal TV licence evasion - problem solved.

Well, that, or make it that people who want BBC services, pay. Bear in mind, when TV receiving licences started, BBC were the only station - actually it started before the BBC were a station even and really was a radio receiving licence. But for some time it was only people accessing BBC services that paid a licence fee.

But either way - public service or paid for service - it should be one or the other not this convoluted legal and administrative nightmare.

Cynical

Let's be cynical for a moment - why now and why this proposal?

The now is kind of down to the existing funding model becoming more and more convoluted and unworkable. That is pretty easy. That said, this is probably just convenient as could be said any time in the last 10 years.

The this is harder - the really obvious answers are either pay for access or public service from general taxation. This proposal is neither. It is creating a new tax, and a means to collect it.

Why would anyone want a new tax - well they are useful - find a way to make a new tax that is (a) justifiable for some public good, and (b) actually less money for 90% of people, and you get away with it.

But what happens when you have a new Home Internet Tax in place - well simple, you can increase it. Boiling frogs. It may be for the BBC now but really is not linked to that even in the existing convoluted ways. So yes, you can increase and extend an Internet access tax as you want, once it is in place.

Clocks

Some time geeks (should I say Time Lords) checked out my clocks.

Seems they are impressed, saying sub microsecond.

I have spent all day trying to improve on that, and I think I have.

The issues are several - the PPS interrupt that captures the time signal works well, but can randomly have extra latency. The original signal can have jitter, drift, and ever sawtooth (actually have not seen this).

What I did not realise is that there is also noticeable clock drift on the processor, probably temperature related.

I previously assumed clean "on the second" PPS. I have changed it so that is used as a reference on longer term (moving average 5 mins) for frequency, and shorter term phase offset tweaks.

This means my per second reference CPU cycle counts change by 1 at a time as things change, the main change being clock frequency drift. This result is reference ticks varying by 4ns or less.

I need to get the Time Lords to check my latest code and see what they find.

Dodecahedron

I was shown a dodecahedron with LEDs inside. Looked great, so decided to have a go.

The principle is not that hard - a PCB strip on the inside of each edge with WS2812 style LEDs, and solder pads on the ends, then a triangle corner piece on each vertex soldered to the strips.

The challenge is making it one continuous LED chain for WS2812. As you can guess - 3 way vertices makes that tricky.

After sleeping on it, I realised I need two types of corner.

First off, the strips, I made the ends consistent.

The idea is the strip has two lanes - one goes through all the LEDs (left to right on that image), and the other just connects from one side to the other with no LEDs. So instead of each edge being one way, it is a two lane road. This allows loops around the edges of the dodecahedron.

Now for the corners - after some thought I decided I need two types, I called Y and C.

The Y type feed each lane to its left. The C type link left and top both ways, and loopback the right. I then designed it so it is just one PCB, with Y one side and C the other side.

If you made all vertices Y then it would be a loop around each pentagon.

But the logic is pretty simple. If you put a dodecahedron on a flat base, you have a bottom, middle, and top.

The middle 10 you put Y corners, and top and bottom you put C corners with the C facing sideways to the next edge around. The effect is a loop or Ys around the middle, with each vertex taking a detour up to the top or bottom and then one edge around the top or bottom before looping back to continue around the middle.

You will see two issues with this.

1. It is two loops, a top hemisphere and a bottom hemisphere, not joined.
2. It is a loop, but WS2812 is a string.

First issue is solved by changing one of the Y middle pieces to a C, facing the C sideways. This C links the two sides making a loop for the entire thing.

Finally the C has an extra pad, and an area where you see to cut a track. Cutting the track breaks the loop, and the pad is where you inject the WS2812 signal.

The exact mapping will depend which C you tapped in to (the obvious one is the extra one on the middle row), and which way around each LED strip is fitted - either work, just change where it is on the string.

Final step was designing a support as a 3D model, 30 pieces that fit together to hold the PCBs. That involved far too much trigonometry for my liking but I worked it out.

Tick Tock

I am pleased to say that my new time servers are in the UK NTP pool now.

Dave has done a nice report on how well they are performing, here.

And this is actually on an ADSL line...

(available from my shop obviously)