Comments on: Photos: inside a Virgin Media cable street cabinet

By: Christopher

Christopher — Thu, 12 Jan 2012 18:36:51 +0000

The coloured labels by the tap points denote attenuation levels; the longer the line to a customer's premises the more attenuation the line will have, simple physics unfortunately. I think they likely have the rows clearly labelled simply for service engineers to quickly understand patch panel layout. A short line with too powerful a signal being sent down it has the potential to cause damage to the CPE (i.e., cable modem) or induce crosstalk. DOCSIS3 (i.e., their 50 MB and 100 MB services) are far less susceptible to this problem (but I still don't rule it out affecting DOCSIS3 connections). Jonbxx on AVForums explained it pretty well in 2007:

It's more to do with the quality of the signal. A cable engineer explained to me that the output power from the green box in the street is set so it's OK for the furthest cabled property from the box. Nearer properties have their signals attenuated in the green box [street cab / dist. box -- Chris] to compensate for the shorter lengths of cable used. Sometimes, the signal can still be a little high at the end of the cable in your house so they put an attenuator on your cable which is what you have there. It's easier to sort the levels at your box than running backwards and forwards from the street cabinet, adjusting levels.

If you want an excellent technical primer on power levels and SNR on the VM cable network, read this on the community forums: http://community.virginmedia.com/t5/Up-to-100Mb-broadband/POWER-LEVELS-amp-SNR-A-TECHNICAL-PRIMER-Nov-2011/td-p/846181. Also useful to read up: http://www.cableforum.co.uk/board/12/33681678-11dbmv-ds-power-level-s.html http://community.virginmedia.com/t5/Fibre-optic-broadband-cable/Using-a-non-Virgin-Media-cable-modem-possible/td-p/10066/page/4 Also of note, discussion about FPAs (Forward Path Attenuators, basically power sinks): http://www.cableforum.co.uk/board/12/33683997-forward-path-attenuators.html. Also if you're reading threads and notice cryptic references to SID or SBD / CAB areas, BOMs etc. these are all industry-specific acronyms; see this thread for an explanation.

By: keith

keith — Thu, 12 Jan 2012 09:21:02 +0000

could anyone tell me what the colour code sections meen!! 29dB 22dB 18dB,, ect ect
we have one outside the house , i have the same thing as my friend next door , yet he is in a differant colour code ????? what is it for PLEASE HELP

By: Christopher

Christopher — Fri, 07 Jan 2011 19:22:39 +0000

They are; there's currently no nationwide FTTC / FTTP in the UK (just VERY limited trials with the promise of future rollout). Virgin Media is today what was once two larger operators (Telewest and NTL) who themselves absorbed many small regional operators, so the network is very fragmented and in quite a few cases very oversubscribed.

The UK cable infrastructure is actually closer to Fibre to the Cabinet than anything else; the national backbones (fibre) run to regional headends, where the Cisco UBRs sit. From there, it's more fibre to the street cabs where it terminates and the signal is transmitted along coax to homes. I was once told this was due to the UK's rather obtuse Health & Safety laws regarding unprotected high power laser light in peoples' homes but I'm not so sure about that (I have a feeling it was technological constraints and cost savings that established the hybrid coax/fibre network the UK has today). Most of the Virgin Media network is DOCSIS3, but this upgrade came very late in comparison to the States.

Aside from "cable" internet, we have a limited rollout of VDSL2+ (by BT, who are calling it BT Infinity, and who are marketing it as "fibre broadband" to compete against Virgin Media). This uses fibre to newly installed street cabs, and VDSL2+ over the customer's existing copper telephone line to their premises. I'm personally on Local Loop Unbundled ADSL2+ (LLU is where ISPs install their own equipment in BT exchanges alongside the original BT equipment, allowing them to move customers' service onto their own network and backhaul as soon as it reaches the exchange, instead of having to transit entirely over the expensive BT nationwide network). Because I'm fortunately <100m from my exchange I get solid 24Mbps download and 2.5Mbps upload with Annex M enabled

By: terrel

terrel — Fri, 07 Jan 2011 17:46:09 +0000

These fiber optic look coaxial cable are they?

By: richard

richard — Wed, 06 Oct 2010 21:54:47 +0000

Hello Chris ive just about solved my problem by using sound boards having got to the point of desperation and no thanks to virgin media, i've tried every posible way to stop the noise that filters into my home. which i do believe comes from the street cabinets, by using insulation. I did tell vm via letter that i would bring this to public attention if nothing was done. I've also reported the on-going noise pollution to the environmental health but as yet have not received a reply from them.

By: richard

richard — Wed, 06 Oct 2010 21:23:34 +0000

hello chris ive just about solved my problem useing sound boards having got to the point of desperation and no thanks to virgin media send me an e mail if you still need a solution i tried evry way posible useing insulation i told vm that i would bring this to public attention if nothing was don ime now makeing it my mission to make a big noise about this all leagle of course vm will wish they had nevver upset me i nearly got devorced through this the pure uncaring ignorance of vm is unbeleivable i anyway hope your ok i know what this can do to people richard

By: Christopher

Christopher — Wed, 04 Aug 2010 12:25:15 +0000

Likewise, I love seeing inside things, underneath covers, what people don't normally see. I went to a CD pressing plant in Blackburn in 2007 (with my work) and I was utterly transfixed, glad I took my camera because the place was shut down a year later by its German owners!

By: sheena doran

sheena doran — Wed, 04 Aug 2010 12:01:37 +0000

Hi there, I have the same problem with a noisy box outside my garden, it hums louder and softer during the day, I have been chatting with a neighbour just yesterday, who has been in touch with the local radio station, local MP and Virgin themselves, she had no joy, I did suggest to her that maybe if we got a few signatures from the neighbouring houses and pass them onto Virgin, it may help our case. I havent written yet myself, but will be this week, its second on my list as at the moment I have a central networks sub station and alleyway to it at the bottom of my garden which is full of thistles and constantly contaminates my garden with weeds..... I have been past various Virgin boxes and noticed how quiet they are in comparison ( not that im an anorak or anything,! ) I will try the "saw someone tampering" ploy and see if I get anywhere, thanks for the tips. By the way I love to see the pics of the inside of things, very interesting, and it bought a memory back from my child hood ( 1060's) that I 'd forgotten, my brother used to regularly stand facinated behind the post office men with thier morris or viva vans(i think) when they were repairing the boxes in the street, they'd give him some of the old bits to play with, and we'd call the little wires with blobs on "telegoons" !!... ..sheena.

By: Dave

Dave — Sat, 24 Jul 2010 18:45:24 +0000

Hello there Chris, thank's for your reply. I did threaten them with talk of me going to my local MP and local radio station and they did get back to me with a promise that an engineer would be out within 48hrs, which he was, so I did get some satisfaction in the end. They told me that the e-mails I had sent didn't get through as there was a breakdown in the system (yeh!) Perhaps a man from Mars answered my phone calls. Anyway thank's for taking an interest. Dave

By: Christopher

Christopher — Thu, 15 Jul 2010 17:18:04 +0000

Hi Dave,

Is the humming really loud? If so the Council might be willing to get involved if it's distracting the peace of you and others around you. Environmental Protection Officers (i.e. noise assessment officers) can come out and install noise measuring equipment if it's really loud - sometimes they'll just do a spot check and go yes/no based on their experience.

If it sounds like a transformer on its way out or something which is not operating within normal parameters, it might be worth ringing VM and reporting the equipment as faulty - what might make them move is if you call them and report having seen someone tampering with the equipment inside the box. As that could have resulted in peoples' service being affected, I expect they'd be more inclined to send an engineer out to take a look (at which point he would likely discover the faulty component).

Can you tell roughly which component's sick from where the noise is emanating from?