So on the Island where i live we have a small BT exchange and for years iv’e been curious to what’s inside. After many times asking my local BT engineer i always got the same response “That’s top secret mate!”
Last year about this time he forgot the key and had to force the door open to fix some shit, I caught wind of this and thought heres my chance to find out. I waited till he fled the island to go home and took my torch for a wonder inside. Here’s what i found.
If any of you can identify any of the technology please spill the beans.
the bit with the old style telephone is the engineers test desk. it still has a UAX (Unattended Automatic Exchange) test set (the bit in the wooden box with all the keys which looks like it is from 1950s.
below it are test points for both copper and fibre circuits.
Alas, the rest of the stuff in there is not especially interesting (or that easy to identify) compared to old skool electromechanical equipment. I’m guessing at it being a local concentrator for a System Y (Ericcson AXE10) exchange, basically all linecards which go to peoples houses are connected with many fibre optic links to a larger Telephone Exchange in the nearest large town and the rest of the processing is carried out there, although BT do also have some custom versions of exchanges they use for the remoter parts of Scotland.
The big blue box is part of the emergency genset and charger for the Exchange battery (usually a load of accus at 48-50 volts. These used to be individual 2 volt ones but might now just be 4 x 12V like large leisure batteries.
below is what these buildings used to contain (you might well have seen a lot of spare space in there as the digital stuff is often more compact)
Lot’s of old cool stuff eh. this island runs 5mb max internet speed. some peeps have virgin and sky phones and broadband, i guess it all runs through this also?
Many of the UAX buildings across the country are still in operational use but with digital equipment inside (a few have been superseded and they occasionally get sold off to be converted into houses), BT have just had fibre brought to them as well as the original copper cables; after all the big hole in the ground and battery backed electricity supplies are all still there.
if VM supply cable TV as well for the area they may have their own exchange and CATV head end elsewhere but it will still link into the BT network via fibre at some point. The broadband for your area certainly does still connect to the original exchange, even VDSL would have the fibre end terminating in there at some point.
In all rural areas of the UK (and most likely elsewhere in Europe) every telecoms service (including mobile phone base stations) still connects to exchanges like this.
Although the level of secrecy about BT equipment is often exaggerated especially by Openreach chaps who worked during 1980s it is classed as critical national infrastructure for this reason, as if anything goes wrong in there 999/112 service can be interrupted (there are usually two seperate control systems present so if one crashes (which does occasionally happen) only half the circuits are knocked out, and to be fair BT deal with major stuff like that very quickly indeed (a very brainy lass I know round here was on 24/7 call at one point to sort things like that out if it happened in the Eastern region)
having looked more closely at the photos (which are just the right resolution to be interesting but not quite sharp enough to present a real security risk) its actually quite smart the way BT have built everything in such a way that the old still works alongside the new.
The 711 dial telephone and the UAX test set appear to have been kept there for a reason (other than it being inconvenient to haul them out or for being “fashionable retro”).
They may well still be used to check that copper circuits have not been cut through or knackered in any way (the modern hand held computerised kit is just an automated version of it) and could still be used today by Openreach engineers to communicate with the nearest large town to restore service, even when everything else may well have gone completely tits up and whatever poor blighter lands up in there is holed up inside in filthy weather having to shout to the control room over the noise of the genset engine (although they have enclosed it to keep the noise level down a bit, I hope for the sake of whoever might land up with such a job the exhaust is good…)
You can hear stuff running from outside, as for the weather. we just 50mph gusts and a few of the island folk had some connection issues. it’s not uncommon. the phone and uax thing look pretty cool in there!i’m sure they’ll still be there in the next 10 years too.
the ventilator fans for modern equipment would certainly stil be audible from outside (similar with VM street cabinets and some BT VSDL ones if you walk past them when its quiet).
I’d actually forgotten how noisy it was inside a pre-digital exchange with electromechanical selectors and relays, last time I saw one was in 1987 as I’d managed to get my high school to arrange with BT for me and some other lads from school who were interested in tech to visit various BT exchanges.
I was lucky enough then to live in a bit of SE England which had all the different types and was just in the middle of the changeover from analogue to digital switching.
This is what would have been inside there until possibly the mid 1990s (apologies for poor quality of the video, it was originally made in 1989!). This equipment was finally hauled out as it didn’t accept tone dialling, and lines were often very noisy making the use of modems at any speed above 1200 bps impossible.
Retired BT engineers and other electronics hobbyists (usually the generation just above mine) often restore the UAX13 (as lots of the bits are still relatively easy to find) and it will fit in a large shed.
Some run it on on its own or at railway and transport museums (where a private telephone exchange is very useful for communications amongst the signalling staff)
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