Comment by heraldgeezer a day 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.
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.
Also, every phone had its own physical circuit to the exchange, leading to things like this: https://i.redd.it/ugvoc90k4q5a1.jpg
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).
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.
Crazy. There is also the https://en.wikipedia.org/wiki/Old_Stockholm_telephone_tower#...
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!
> 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.
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.
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.