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Re:Telephone Exchanges in the UK by heraldgeezer on Sunday June 15, 2025 @05:20PM (#44285049)
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.
Re:Telephone Exchanges in the UK by merlynkline on Sunday June 15, 2025 @06:44PM (#44285449)
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.
Re:Telephone Exchanges in the UK by lxgr on Sunday June 15, 2025 @07:24PM (#44285605)
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!

Re:Telephone Exchanges in the UK by pests on Sunday June 15, 2025 @10:18PM (#44286182)
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.
Re:Telephone Exchanges in the UK by userbinator on Sunday June 15, 2025 @08:51PM (#44285929)
Also, every phone had its own physical circuit to the exchange, leading to things like this: https://i.redd.it/ugvoc90k4q5a1.jpg
Re:Telephone Exchanges in the UK by heraldgeezer on Sunday June 15, 2025 @09:12PM (#44286000)
Re:Telephone Exchanges in the UK by steelegbr on Monday June 16, 2025 @06:25AM (#44288158)
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).

Re:Telephone Exchanges in the UK by redjet on Monday June 16, 2025 @10:52AM (#44290155)
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.

Re:Telephone Exchanges in the UK by miki123211 on Monday June 16, 2025 @12:48AM (#44286693)
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.

Re:Telephone Exchanges in the UK by psychotaurusaqu on Sunday June 15, 2025 @06:25PM (#44285374)
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.
Re:Telephone Exchanges in the UK by ipdashc on Monday June 16, 2025 @01:34AM (#44286859)
> 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.