My dad was a telephone engineer/manager with GTE in the US. As a kid in the mid 1970s he used to take me with him to the local exchange building to deliver donuts to the guys on duty (he was that kind of boss). The security was interesting - there was a tube built into the masonry with a 90 degree angle that had a mirror. He would pick up the phone on the outside wall and say his name and an identifying number and then the door would buzz open. The building was a few stories tall and had no windows, which I think was a Cold War thing.
We would deliver the donuts to the break room which usually had at least one guy smoking in it (it was the '70s). A couple of times we went into the switching room which still had rotary dial switches clacking away as people dialed in numbers. There was an overwhelming smell of ozone in the room. It was all very cool to 5 year old me.
thorin 10 hours ago [-]
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 22 hours 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 18 hours 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.
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.
Neil44 8 hours ago [-]
I was going to post this, I had a fab time in that little room with all the click-clacking gear.
biofox 23 hours ago [-]
This is an impressive feat of cataloguing!
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 22 hours 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.
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.
ajb 6 hours ago [-]
U.S.S.R. military had far more complete maps of many parts of the U.K. than Ordnance Survey published.
Although amusing, note that its than the Ordnance Survey published. I.E. they had the data, it was just classified. Also, it's fairly clear that the Soviet maps were mostly derived from OS maps. Looking at my street, for example, they have it in a pre-WWII configuration which they could only have got by starting from a rather old OS map. So they clearly only checked for differences in areas they thought important, such as government or military areas - they didn't have people mapping the whole UK. Still it's probably true that one can get more information about certain areas in these Soviet maps than in extant OS maps.
toyg 22 hours 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 21 hours 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)?
razakel 7 hours ago [-]
It also had a restaurant open to the public.
ta1243 7 hours ago [-]
The one place in London you can't see it
bdsa 7 hours ago [-]
My dad (who worked for BT in various positions) claims he was involved with the decision to move the exchange in our/their village from one end to the other. Coincidentally, closer to the end in which we lived, which I gather would have a non-trivial impact on our internet speed.
I think this probably coincides with the time period we got ISDN, very early, and I was amazed by the concept of _always connected_ internet. I can still vividly remember watching GoZilla download a game demo at 7kb/s, stunned and excited.
ricardo81 22 hours 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 11 hours 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.
TorKlingberg 4 hours ago [-]
Interestingly, Cityfibre often reuse the old telephone poles. It means you can get fibre to the home with no digging required. Yay old tech?
unwind 9 hours ago [-]
You meant *asymmetric offering, right?
f4c39012 22 hours 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 21 hours 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 22 hours 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 20 hours 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.
rcxdude 18 hours 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).
danw1979 11 hours 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…
dazzawazza 9 hours ago [-]
Where as in London, where there is at least one house every 8 meters, they were in and out of my street in two days and now we have constant door to door sales people offering deals.
Smells like they "installed" fibre in York to meet a contract/regulation but they really focus on Urban density. Makes sense for them but not for the rest of us.
Affric 21 hours ago [-]
The roadworks during my youth were endless. It was maddening. Never occurred to me that it could have all been telcos.
bloomingeek 6 hours ago [-]
Although I never went into one of these buildings, in the early 80's I was a sub-contractor burying cable for SWB. I was always amazed at all the property they controlled. I had access to all their construction yards, which were spread out all over the city, some of them in the suburbs. Protecting these yards from theft was always a nightmare for them.
jonatron 22 hours 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 11 hours 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.
jonatron 10 hours ago [-]
No, it was just a normal BT exchange in Suffolk
mojo74 7 hours ago [-]
Shout out to Milton Keynes Museum for their archive of handsets old and new as well as interactive examples of telephone exchanges:
I used to live pretty much opposite the village exchange. It was just a very boring and nondescript little building, backed up by the picture on that website. I bet it was much more interesting inside though
bravesoul2 16 hours ago [-]
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.
GJim 9 hours ago [-]
No.
It certainly wasn't a voting system. Rather, it was a decent enough system used to help gauge demand in a given area. (Unsurprisingly, there was a lot of demand for ADSL in university towns, and much less in retirement-town-by-the-sea).
dboreham 17 hours 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!
arethuza 9 hours ago [-]
I walked past there the other day (on the Fife coastal path) and wondered what the shabby building was - I had assumed it was an abandoned light industrial unit.
heraldgeezer 22 hours 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 21 hours 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 14 hours 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.
Generally yes and even today, if you've got a twisted pair, it's that down to the exchange. Though party lines were also a thing a very long time ago.
There were also specialist circuits (e.g. EPS) where you had a physical line from end to end (with a couple of amps along the way on longer runs).
redjet 4 hours ago [-]
That mention of EPS takes me back, we used to use it all over the place to form basic hub-and-spoke networks in areas where we had lots of small sites that would all connect to a single exchange. It would generally bounce along at 2Mbps which wasn't bad in those days.
We also had some large campus type sites where we would sometimes implement EPS to do LAN extension over the onsite twisted pair as it was cheaper than installing fibre and just about fast enough.
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 17 hours 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 14 hours 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 21 hours 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.
We would deliver the donuts to the break room which usually had at least one guy smoking in it (it was the '70s). A couple of times we went into the switching room which still had rotary dial switches clacking away as people dialed in numbers. There was an overwhelming smell of ozone in the room. It was all very cool to 5 year old me.
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...
https://avoncroft.org.uk/avoncrofts-work/special-collections
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.
Although amusing, note that its than the Ordnance Survey published. I.E. they had the data, it was just classified. Also, it's fairly clear that the Soviet maps were mostly derived from OS maps. Looking at my street, for example, they have it in a pre-WWII configuration which they could only have got by starting from a rather old OS map. So they clearly only checked for differences in areas they thought important, such as government or military areas - they didn't have people mapping the whole UK. Still it's probably true that one can get more information about certain areas in these Soviet maps than in extant OS maps.
> 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
I think this probably coincides with the time period we got ISDN, very early, and I was amazed by the concept of _always connected_ internet. I can still vividly remember watching GoZilla download a game demo at 7kb/s, stunned and excited.
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…
Smells like they "installed" fibre in York to meet a contract/regulation but they really focus on Urban density. Makes sense for them but not for the rest of us.
I did that tour around the same time and it was fascinating ! right in the middle of the 21CN (ethernet core network) transition.
https://miltonkeynesmuseum.org.uk/collections/view-our-colle...
It certainly wasn't a voting system. Rather, it was a decent enough system used to help gauge demand in a given area. (Unsurprisingly, there was a lot of demand for ADSL in university towns, and much less in retirement-town-by-the-sea).
It's really surprising to me how little uptake 2600 ultimately ended up having.
There were also specialist circuits (e.g. EPS) where you had a physical line from end to end (with a couple of amps along the way on longer runs).
We also had some large campus type sites where we would sometimes implement EPS to do LAN extension over the onsite twisted pair as it was cheaper than installing fibre and just about fast enough.
"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?