Telecom roadside cabinets and junction boxes etc

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scottjpalmer

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#20368 23-Mar-2008 18:54

Can someone who knows enlighten me as to how Telecom wires get from the exchange to my house :-) I assume it varies greatly based on the age of the suburb and the number of houses being served.

To narrow it down a little to specifically what I want to know, although a general overview would be great . . .

What connects a cabinet like this to the exchange? What physically gets done inside this cabinet?

This here green box, is it a modern day version of the grey PVC downpipe sized tubes that are around the place? Is it's contents purely passive or are there smarts in there? This particular one feeds 3 - 5 houses maybe up to 7. Is it fed with the same number of pairs as the houses it services?

The pair of wires that terminate at the demarc, they physically (ie no joiners) run as far as the nearest little green box like above or nearest grey PVC tube yes? If a new house or 2 suddenly get built on the back of a section behind another house is that when a grey / green junction box get installed?

So up the side of a standard street in suburbia, under the ground, there is a big wad of potentially 100s of pairs?

I'll stop now, for now :-)

Thanks!

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cr250bromo

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#118285 23-Mar-2008 22:53

Historically the cabinets were nothing more than a passive copper cross connection point, no smarts in any of them at all.

That cabinet you show there (PUK/AD) will have 200+ copper pairs running underground from it to the MDF at the Pukekohe telephone exchange. Then all of the nearby streets to that cabinet will have cables ranging from 25 - 50 pairs terminating in the cabinet. Obviously the number of pairs in the local streets depends on population density, demand for telephone services, historical factors and so on.

The small green box you show would have the cable serving the street looped up into it, so all 25 - 50 pairs would be available there.

When new phone service is requested, an exchange port would be allocated and a number assigned. Then at the exchange building on the MDF the tech would jumper a connection from the allocated exchange port to a free pair in the nearest cabinet to where service is required. eg they might connect to PUK/AD pair number 151. Then within the cabinet they would connect that pair to a free pair on the cable serving the street where service is required. Finally that pair would be connected in the small green box to the house/business requesting phone service.

The first non passive cabinets appeared in the late 80s/early 90s (particularly in rural areas where older electrical mechanical exchanges and party lines were taken out of service). Telecom would feed equipment in the cabinet from the exchange via fibre or copper using one or more 2mbit digital circuits. Then the subscribers fed by the cabinet would get their dialtone from this equipment.

I don't know what equipment they used in NZ but Google for SLC96 (which were very common in the USA). These systems were also installed for new developments/subdivisions well past 2000 as well as being used where there was a sudden massive demand for new phone lines but insufficient free pairs - anyone remember people at flash new subdivisions "fed via fibre" complaining they couldn't get DSL? They probably didn't notice but their 56kbit dialup modem connections were probably pretty good given their local loop would be from their house to their cabinet.

Remote/rural areas and newer subdivisions that have DSL currently are generally being fed by conklin devices within the cabinets, however I gather the uplink capacity of these is quite limited. I guess that brings us forward to now with the impending "cabinetisation", ie putting a decent ADSL2+ DSLAM into the cabinet and feeding it with a decent sized uplink.

Probably enough geek info for now, I'm sure if I've made any errors in the above they will be pointed out by other geeks here. :)

/portunus

scottjpalmer

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#118286 23-Mar-2008 23:19

Cool, thanks!

So how many houses can be served from a cabinet like that? Or to put it another way, in Pukekohe, population 20-25,000, how many cabinets will there be? And then houses and businesses close enough to the Exchange will be connected directly?

Getting out into rural, how far can the copper actually carry standard telephone without the need for cabinets being fed via fibre or otherwise being installed?

Thanks for your help, very very informative!

scottjpalmer

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#118287 23-Mar-2008 23:28

And . . .

I'm moving on Thursday, not very far, pretty sure still off that big cabinet - will they be smart enough to just change my jumper in the roadside cabinet? Or will they start from scratch connecting my naked DSL right back at the exchange?

cr250bromo

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#118299 24-Mar-2008 00:52

No probs, I've always been a bit of a phone geek. :)

With regards to you moving house, yup, as long as your new house is serviced from the same cabinet as your old house they could just rejumper at the cabinet to the cable serving the street your new house is on without needing to visit the exchange, as long as the request for the tech told them what pair number from the exchange you were allocated within the cabinet.

Based on the cabentisation info telecom released recently the average cabinet has around 200 active connections running off it, the largest had 455 active connections and the smallest had 1 (possibly at a new subdivision where not many people had moved in).

There would obviously be more pairs coming into the cabinets from the local streets on the basis that while some houses/businesses need a lot of lines, other locations may not require any lines at all. I guess for Pukekohe there would be quite a mix of urban and rural so difficult to say exactly how many cabinets there would be in total. However the designations start at A and go through to Z, then move onto AA, AB and so on. The first three letters are the exchange the cabinet is connected to, ie PUK in your case, so when you are driving around next keep an eye out for those cabinets, purely out of geek interest of course. :)

Yup the cables serving the streets very close to the exchange would be connected directly and not go via a cabinet. Telecom have said the subscribers near the exchange would not be "cabentised", I think this would include cabinets fairly close to the exchange which would remain passive. Ie if the copper run is short enough there is nothing much to be gained by putting a DSLAM in them.

Runs of copper of 10KM+ are possible, however for long lines you need to add loading coils to the line at intervals which keeps POTS voice services working but stops DSL from working and doesn't help dialup modems. I am not sure what improvements the future holds for the rural/isolated customers on the end of very long runs. Since the Telecom Cabentisation program only covers exchanges with 500 or more lines.

Aloha

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#119355 28-Mar-2008 14:56

Read this blog about TNZ's latest cabinet for ADSL2+ with photos...

http://publicaddress.net/default,4880.sm#post4880

I is a kollege stoodent. Bee nice.