Does this mean that probably somewhere below that tower, there were operator stations that would have allowed any of the 5500 lines to connect to any of the other lines? How many simultaneous calls would that even be? Correct me if I borked this, but 5500!/(2^(5500/2)), perhaps?
It seems plausible that if the phone had only just been invented, you'd initially set up small systems that would in fact allow any line to connect to any line. That'd be fine for maybe even a few dozen lines. But as the image shows, that doesn't scale too well.
Even a large confluence of connections like this would likely still have had local switchboards.
When you made a call, your local operator would have connected you either to a local number on their own board, or to another local board as needed. That second operator would have then connected you to the desired number.
Each board would only have limited connection lines to each other board (or to a branch exchange). So if all the connections from board A to board B (or to the branch exchange) were in use, the caller would have to try again later.
Comments mention multiplexing and that’s not wrong but the real reason for the vast number of wires is amplifiers, or rather the lack of practical ones at the time. You had to transmit at high enough power to overcome losses and still be able to hear at the destination.
Each wire carries just one signal at a power that would easily interfere with others, they needed relatively thick wires separated from each other. You see pictures of poles with lots of cross bars carrying lots of wires in this period.
Once amplification was practical they could use the thin telephone wires bundled together in a cable, each wire carrying a much fainter signal that can be easily amplified as needed.
Amplification existed but it took the vacuum tube to get it affordable and reliable for each circuit to have its own amplification.
When the tower was constructed in 1887, multiplexing technology was probably not available (I'm not so sure of the timeline in Europe). By 1913 it likely would have come into use. However, multiplexing really isn't a factor here, as the tower seems to have been built to serve local loops. Since these loops go to subscriber telephone sets, there's no option for multiplexing without expensive and maintenance-intensive equipment at customer premises. Multiplexing of local loops is called "pair gain" and wouldn't be developed until later, and it was never really that popular in most phone systems. Outside of suburban areas, it's typical that each copper pair runs directly to the exchange. Historically, and today, there is rarely any active equipment (or since the 1950s or so even passive conditioning) on local loops, they're just wires from the exchange to the phone.
As for why you didn't see similar constructions in other cities, this was definitely an unusually large telephone office for the time. In the US, a city exchange of the late 20th century would usually have just hundreds of lines, many of them multi-party. Telephone companies scaled up by building more exchanges, rather than a single very large one. When they got into these kinds of subscriber numbers at an exchange, the F1/F2 cable scheme was in use to avoid this kind of wiring. It does seem to be the case that telephone adoption was unusually rapid in Sweden, I find one (poorly sourced) claim that there were some 4,800 telephone subscribers in Stockholm in 1886 which would very likely make it the most telephone-rich city in the world. The situation of the tower seems to have developed in part because its builder, Allmänna, was consolidating the Stockholm telephone market through acquisitions and made a decision to centralize the many acquired customers onto on exchange.
What I'm a little confused about here is the lack of cables. The other big reason you didn't see constructions like this in the US, even in places like New York City, is because subscriber loops were quickly moved into lead-sheathed, paper-insulated multi-pair cables. These could contain hundreds of pairs. Cables were pretty much reaching maturity when this tower was built. I am curious as to the reason that multi-pair cables were not adopted more quickly in Stockholm, but it may be as simple as the considerable investment in this tower making open wire the preferred option for its short lifespan. In any case, the common claim that underground cables obsoleted the tower rings hollow to me, or at least misses an important detail, as aboveground cables were already in use in the 1880s. I suspect that modernization to cables was just deferred in Stockholm until it happened to also make sense to move to duct or pipe systems. In the US, it was more common that telephone exchanges switched to overhead (aerial) cable to manage exactly the wire sprawl issue that this tower exemplifies, and then only later (if ever) started to bury cables.
As someone obsessed with Networking and Networking Topology I am so so fascinated by analog telephone networks. Just the idea of long-distance connections being made via physical wires connecting at switches by human operators feels so raw. I can't even imagine such a thing. When I was younger analog telephone was being phased out. I still remember my dad having to go buy calling cards at convenience stores so he could make long distance calls back home. And then one day there were no more calling cards.
I can imagine lots of lessons learned from telephone networking helped shape ideas around computer network design.
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[ 4.3 ms ] story [ 55.1 ms ] threadhttps://www.reddit.com/r/HalfLife/comments/e809fn/cant_help_...
[1] https://en.wikipedia.org/wiki/Optical_telegraph
https://en.wikipedia.org/wiki/Redevelopment_of_Norrmalm?wpro...
It seems plausible that if the phone had only just been invented, you'd initially set up small systems that would in fact allow any line to connect to any line. That'd be fine for maybe even a few dozen lines. But as the image shows, that doesn't scale too well.
When you made a call, your local operator would have connected you either to a local number on their own board, or to another local board as needed. That second operator would have then connected you to the desired number.
Each board would only have limited connection lines to each other board (or to a branch exchange). So if all the connections from board A to board B (or to the branch exchange) were in use, the caller would have to try again later.
Still, pretty astronomical.
Each wire carries just one signal at a power that would easily interfere with others, they needed relatively thick wires separated from each other. You see pictures of poles with lots of cross bars carrying lots of wires in this period.
Once amplification was practical they could use the thin telephone wires bundled together in a cable, each wire carrying a much fainter signal that can be easily amplified as needed.
Amplification existed but it took the vacuum tube to get it affordable and reliable for each circuit to have its own amplification.
As for why you didn't see similar constructions in other cities, this was definitely an unusually large telephone office for the time. In the US, a city exchange of the late 20th century would usually have just hundreds of lines, many of them multi-party. Telephone companies scaled up by building more exchanges, rather than a single very large one. When they got into these kinds of subscriber numbers at an exchange, the F1/F2 cable scheme was in use to avoid this kind of wiring. It does seem to be the case that telephone adoption was unusually rapid in Sweden, I find one (poorly sourced) claim that there were some 4,800 telephone subscribers in Stockholm in 1886 which would very likely make it the most telephone-rich city in the world. The situation of the tower seems to have developed in part because its builder, Allmänna, was consolidating the Stockholm telephone market through acquisitions and made a decision to centralize the many acquired customers onto on exchange.
What I'm a little confused about here is the lack of cables. The other big reason you didn't see constructions like this in the US, even in places like New York City, is because subscriber loops were quickly moved into lead-sheathed, paper-insulated multi-pair cables. These could contain hundreds of pairs. Cables were pretty much reaching maturity when this tower was built. I am curious as to the reason that multi-pair cables were not adopted more quickly in Stockholm, but it may be as simple as the considerable investment in this tower making open wire the preferred option for its short lifespan. In any case, the common claim that underground cables obsoleted the tower rings hollow to me, or at least misses an important detail, as aboveground cables were already in use in the 1880s. I suspect that modernization to cables was just deferred in Stockholm until it happened to also make sense to move to duct or pipe systems. In the US, it was more common that telephone exchanges switched to overhead (aerial) cable to manage exactly the wire sprawl issue that this tower exemplifies, and then only later (if ever) started to bury cables.
This article has more photos of the tower, but unfortunately not much more technical history: https://rarehistoricalphotos.com/the-stockholm-telephone-tow...
And this includes some photos of other parts of the Stockholm telephone network. The tower was not the only impressive construction required to manage this many open-wire pairs: https://thehistoryinsider.com/when-the-sky-over-stockholm-wa...
I can imagine lots of lessons learned from telephone networking helped shape ideas around computer network design.