My dad worked at BT and used to take me to different exchanges at the weekend normally on Saturday mornings. I guess he claimed a day in lieu for working a couple of hours and then we went for lunch or pottered around the shops. In there were all sorts of interesting things. Piles of discarded electronics of various eras. Several computers and terminals for connecting to mainframe systems. I remember a Sinclair QL and Amstrad PCWs I think. He would let me play around with the terminals, no idea what OS was on there maybe VAX or VMS, use the printers and Microdrives. I was really interested in all that stuff as a kid but didn't really have anyone to learn from as my dad was more of a lineman, having started in the Royal Signals. Fun times!
tdeck · 13h ago
If anyone is interested in telephone exchange technology at all, I highly recommend checking out the Connections Museum in Seattle. They have multiple eras of electromechanical switching equipment up and running, and a huge collection of cool old phones, teletypes and payphones. They also have a great YouTube channel with very knowledgeable people.
I feel like they're not well known and there's no place like it!
tobinfekkes · 8h ago
Another excellent museum is the Kodiak Military History Museum at Fort Abercrombie, on Kodiak Island, Alaska.
It has some old working telephone and teletype systems. You can watch the physical switching equipment do its magic. It is truly awesome. The raw speed and accuracy of the mechanical systems is almost unbelievable.
You can go and play with an old branch exchange, with all the whistles and er, bells at "This Museum is (not) Obsolete". Run by Sam from Look Mum No Computer. If you're ever near Ramsgate in the UK.
Considering the telecom system is at the bedrock of almost all modern technologies, it really doesn't get enough love or attention in the public mind.
The dull derelict-looking, and often graffitied, buildings that house the system doesn't reflect just how cool the infrastructure is.
rwmj · 12h ago
My physics teacher in the 1980s (sadly RIP a few years ago[1]) told me that the location of telephone exchanges was a UK state secret. The theory was that the Russians would nuke them destroying the country's ability to communicate, but as their location was a secret that outcome could be prevented. 40+ years on, I wonder if any of that was actually true?
> the location of telephone exchanges was a UK state secret
I found myself wondering whether the locations of electricty substations powering critical infrastructure might count as "secret", for instance the three[0] substations that power Heathrow Airport.
Obviously one of them isn't secret any more more, having gone up in flames rather spectacularly on 21 March 2025.
It wasn't very secret, at least for local exchanges as I went into many in the north-east of England with my dad as a kid.
JdeBP · 10h ago
In hindsight, that does seem a little ridiculous; yet it was indeed the thinking. One could see where the exchanges were by simple dint of visiting a place. Soviet spies would just have had to walk around a bit.
Of course, nuclear weapons wouldn't even have had to specifically target exchanges in order to disrupt electronic communications as they already were by the 1980s.
It was amusing to learn a decade ago that the U.S.S.R. military had far more complete maps of many parts of the U.K. than Ordnance Survey published. Apparently down to Soviet spies just walking around a bit, playing tourist.
toyg · 12h ago
The dullness is eerily consistent. Even in the age of privatisation, when everything is a brand, these buildings are devoid of markings. So it might well be true, we just stopped worrying about it once the cold war was officially over (once we realized the Russians already knew everything they needed anyway).
snthd · 11h ago
>As our [1978] trial started, witness after witness from security sites tried to claim that openly published information was in fact secret. In a typical interchange, one Sigint unit chief was shown a road sign outside his base:
> Q: Is that the name of your unit?
> A: I cannot answer that question, that is a secret.
> Q: Is that the board which passers-by on the main road see outside your unit’s base?
> A: Yes.
> Q: Read it out to the jury, please.
> A: I cannot do that. It is a secret.
>Official panic set in. The foreign secretary who GCHQ had bullied into having us accused of spying wrote that “almost any accommodation is to be preferred” to allowing our trial to continue. A Ministry of Defense report in September 1978, now released, disclosed that the “prosecuting counsel has come to the view that there have been so many published references to the information Campbell has acquired and the conclusions he has drawn from it that the chances of success with [the collection charge] are not good.”
>My lawyer overheard the exasperated prosecutor saying that he would allow the government to continue with the espionage charge against me “over [his] dead body.” The judge, a no-nonsense Welsh lawyer, was also fed up with the secrecy pantomime. He demanded the government scrap the espionage charges. They did.
GCHQ and Me, My Life Unmasking British Eavesdroppers -- Duncan Campbell
Wait, what? What else were people supposed to assume about the purpose of a huge tower with very noticeable horn antennas (widely used for long-distance phone calls over line-of-sight microwave at the time)?
oniony · 1h ago
The Avoncroft museum of buildings in Bromsgrove, near Birmingham, UK, is worth a visit. They have a bunch of old telephone boxes all working and hooked up to an exchange they have on site. I spent like an hour talking to the guy in there about it all, pretty fascinating.
If you find yourself in that part of the world, there's also a carpet museum in Kidderminster, and the Black Country Museum in Dudley. A little bit further north and then there are a slew of industrial museums in Ironbridge.
ricardo81 · 13h ago
Our old countries (and their tech) building on top of old.
Developing countries have less of a hassle with implementing something based on state of the art.
Lots of hassles with getting new phone lines, new power lines et al in the UK based on old agreements and a nationalised infrastructure. Please stop digging up roads and everything for arbitrary telecoms companies based on some deregulation, some collaboration please :-)
jansper39 · 1h ago
No thank you, my Cityfibre connection is 2/3 of the cost of a BT hosted one and is 150Mb up and down, instead of BT's asynchronous offering. Installed in a couple of days of ordering too.
f4c39012 · 12h ago
someone from the local gas company told me that the reason the utilites don't work together is that they can't because of rules - electric and gas need to be kept separate for safety, and the surrounding soil means water leaks can be absorbed away from other utilities' pipework. I didn't dig any deeper
matt-p · 11h ago
Like most things that's half true.
It's true you don't want a telecom worker laying a gas pipe, however you can coordinate this stuff if you want to. Typically the deepest utility works first then backfills just to the level of the next utility and so forth. However timing is critical, the second utility must be ready to work as soon as the first is done and so on.
The biggest reasons they don't is mostly (in this order)
-They can't time their work to be at the same time as 3 other utilities.
-They can't work out cost and liability sharing, if the last utility to work does the reinstatement and takes liability for it then the telecom company will always pay while electric typically won't pay anything as it's in the middle. The legal demarcation between utilities is also much less clearly defined.
-Contractors typically do all work, not actual utilities and it's in their best interests to dig the road up five times (one for each utility) rather than just once. The same goes for everyone else who gets paid when the road is opened; including, often, the local government (for permits).
kimixa · 12h ago
I feel there's a generation of Brits burned the wave of random telecoms companies digging up major roads for years for cable, only for the results to be pretty much useless by the time it's done as ADSL and existing POTS lines could do pretty much the same thing without any more digging.
The words "Diamond Cable" still fill me with dread to this day. They dug up half our village to then offer no service.
JdeBP · 10h ago
I know someone who is still waiting for City Fibre, who dug up xyr road last year, to get around to actually offering a service.
danw1979 · 1h ago
A local fibre co here in York dug a cable to all the way my parent’s farm house, about 250m outside the nearest village (and probably even further into the village to reach the PCP), then left the cable coiled up on the outside of their property and haven’t done anything further with it in over a year.
I’ve heard other similar stories from friends in the city too.
It’s almost like there’s money for the infrastructure but not for the staff required to actually run it as a service…
rcxdude · 9h ago
City Fibre has worked alright around where I live. It was also about a year or so after most of the digging (now a few years ago), but it's been nice to have actual fibre internet (through a different ISP, since they just do the infrastructure).
Affric · 11h ago
The roadworks during my youth were endless. It was maddening. Never occurred to me that it could have all been telcos.
jonatron · 13h ago
I visited an exchange back in 2009, when Local loop unbundling (LLU) on ADSL was big, and fibre was limited to large business and datacentres. The huge generator was probably more interesting than the racks of concentrators. I'm not sure how much battery back-up power time the new PON systems have, I assume less than a generator backed system.
danw1979 · 1h ago
Was this the BT demo exchange somewhere in Essex ? Bishop Stortford maybe ?
I did that tour around the same time and it was fascinating ! right in the middle of the 21CN (ethernet core network) transition.
I recall there was a voting system by BT circa 2002 to get your local exchange upgraded to "broadband" (i.e. not just 56k dialup) if it wasn't already.
dboreham · 7h ago
Interesting to see Kinghorn in the database (01592-89) because I toured the exchange as a child sometime in the late 1970s before it was brought into service (my Dad knew a bloke who worked for GEC). iirc it was a TXE4 system then, or at least of that generation. Building in a very poor state of repair now. Probably hasn't been painted since 1979!
heraldgeezer · 12h ago
Really, its own internet system before the internet. Massive load of calls. The routing has to be correct. I never understood it before working in telecom, but phones numbers are unique... for routing, like IP-addresses. And it could never go "down". In the 80s it was all digial too (Ericsson switches) and had to be real-time.
merlynkline · 11h ago
Before modern digital electronics, telephone numbers were literal routes - when the turned dial on your phone ran back to zero, a corresponding 10-pole motorised rotary switch at the exchange turned and connected you to one of 10 lines. This connected you to another such rotary switch for the next digit, until eventually you were connected to the final destination. The ingenious Strowger exchange.
miki123211 · 5h ago
And when there was a bug in that complex and vast routing system somewhere, it was completely unfixable. Not without million-dollar hardware replacements at least.
It's really surprising to me how little uptake 2600 ultimately ended up having.
Invented by a paranoid undertaker out of business interest, apparently:
"Strowger, an undertaker, was motivated to invent an automatic telephone exchange after becoming convinced that the manual telephone exchange operators were deliberately interfering with his calls, leading to loss of business."
I wonder if the phone company was actually out to get him!
pests · 7h ago
I've heard this story before and it included the detail that his competitor's wife worked as an operator at the exchange, and his worry was she would direct calls for an undertaker to her husband instead of himself.
ipdashc · 4h ago
> Really, its own internet system before the internet. ... for routing, like IP-addresses.
There's a great video from Connections Museum (mentioned further up the thread) where they're going through the operation of, I want to say, one of those crossbar switches? And they start using terminology like "routing table", "longest-prefix matching", and "default route", which all sounds well and good, until you realize they're talking about systems that existed decades before the Internet or even ARPANET, all electromechanical... Dope stuff. Cool to see how things rhyme even as they change.
psychotaurusaqu · 11h ago
Combination of Ericsson and GEC/Plessey/BT "System X" (see https://en.wikipedia.org/wiki/System_X_(telephony)). Erisson AXE10 was known as "System Y" in the UK and a hedge against buying exclusively System X equipment.
https://www.telcomhistory.org/ConnectionsSeattle.html
https://m.youtube.com/@ConnectionsMuseum
I feel like they're not well known and there's no place like it!
It has some old working telephone and teletype systems. You can watch the physical switching equipment do its magic. It is truly awesome. The raw speed and accuracy of the mechanical systems is almost unbelievable.
https://this-museum-is-not-obsolete.com/
https://www.amberleymuseum.co.uk/explore/explore-communicati...
https://www.amberleymuseum.co.uk/explore/explore-communicati...
Considering the telecom system is at the bedrock of almost all modern technologies, it really doesn't get enough love or attention in the public mind.
The dull derelict-looking, and often graffitied, buildings that house the system doesn't reflect just how cool the infrastructure is.
[1] https://johnchess.blogspot.com/2019/11/david-welch-1945-2019...
I found myself wondering whether the locations of electricty substations powering critical infrastructure might count as "secret", for instance the three[0] substations that power Heathrow Airport.
Obviously one of them isn't secret any more more, having gone up in flames rather spectacularly on 21 March 2025.
[0] "Heathrow relies on three electricity substations" https://www.bbc.com/news/articles/c6283577llqo
Of course, nuclear weapons wouldn't even have had to specifically target exchanges in order to disrupt electronic communications as they already were by the 1980s.
It was amusing to learn a decade ago that the U.S.S.R. military had far more complete maps of many parts of the U.K. than Ordnance Survey published. Apparently down to Soviet spies just walking around a bit, playing tourist.
> Q: Is that the name of your unit?
> A: I cannot answer that question, that is a secret.
> Q: Is that the board which passers-by on the main road see outside your unit’s base?
> A: Yes.
> Q: Read it out to the jury, please.
> A: I cannot do that. It is a secret.
>Official panic set in. The foreign secretary who GCHQ had bullied into having us accused of spying wrote that “almost any accommodation is to be preferred” to allowing our trial to continue. A Ministry of Defense report in September 1978, now released, disclosed that the “prosecuting counsel has come to the view that there have been so many published references to the information Campbell has acquired and the conclusions he has drawn from it that the chances of success with [the collection charge] are not good.”
>My lawyer overheard the exasperated prosecutor saying that he would allow the government to continue with the espionage charge against me “over [his] dead body.” The judge, a no-nonsense Welsh lawyer, was also fed up with the secrecy pantomime. He demanded the government scrap the espionage charges. They did.
GCHQ and Me, My Life Unmasking British Eavesdroppers -- Duncan Campbell
https://theintercept.com/2015/08/03/life-unmasking-british-e...
https://en.wikipedia.org/wiki/Anchor_telephone_exchange
https://en.wikipedia.org/wiki/Guardian_telephone_exchange
https://avoncroft.org.uk/avoncrofts-work/special-collections
Developing countries have less of a hassle with implementing something based on state of the art.
Lots of hassles with getting new phone lines, new power lines et al in the UK based on old agreements and a nationalised infrastructure. Please stop digging up roads and everything for arbitrary telecoms companies based on some deregulation, some collaboration please :-)
It's true you don't want a telecom worker laying a gas pipe, however you can coordinate this stuff if you want to. Typically the deepest utility works first then backfills just to the level of the next utility and so forth. However timing is critical, the second utility must be ready to work as soon as the first is done and so on.
The biggest reasons they don't is mostly (in this order)
-They can't time their work to be at the same time as 3 other utilities.
-They can't work out cost and liability sharing, if the last utility to work does the reinstatement and takes liability for it then the telecom company will always pay while electric typically won't pay anything as it's in the middle. The legal demarcation between utilities is also much less clearly defined.
-Contractors typically do all work, not actual utilities and it's in their best interests to dig the road up five times (one for each utility) rather than just once. The same goes for everyone else who gets paid when the road is opened; including, often, the local government (for permits).
The words "Diamond Cable" still fill me with dread to this day. They dug up half our village to then offer no service.
I’ve heard other similar stories from friends in the city too.
It’s almost like there’s money for the infrastructure but not for the staff required to actually run it as a service…
I did that tour around the same time and it was fascinating ! right in the middle of the 21CN (ethernet core network) transition.
It's really surprising to me how little uptake 2600 ultimately ended up having.
"Strowger, an undertaker, was motivated to invent an automatic telephone exchange after becoming convinced that the manual telephone exchange operators were deliberately interfering with his calls, leading to loss of business."
I wonder if the phone company was actually out to get him!
There's a great video from Connections Museum (mentioned further up the thread) where they're going through the operation of, I want to say, one of those crossbar switches? And they start using terminology like "routing table", "longest-prefix matching", and "default route", which all sounds well and good, until you realize they're talking about systems that existed decades before the Internet or even ARPANET, all electromechanical... Dope stuff. Cool to see how things rhyme even as they change.
and this
https://www.academia.edu/39809466/System_X_The_history_of_th...
by http://www.kingdom-technology.co.uk/malcolmhamer.php
Is their content really so sensitive that it must be "protected" to such a degree?