I’m reminded of when an old AT&T building went on sale as a house, and one of its selling points was that you could get power from two different power companies if you wanted. This highlighted to me the level of redundancy required to take such things seriously. It probably cost the company a lot to hook up the wires, and I doubt the second power company paid anything for the hookup. Big Bell did it there, and I’m sure they did it everywhere else too.
Edit: I bet it had diesel generators when it was in service with AT&T to boot.
> I bet it had diesel generators when it was in service with AT&T to boot.
20 to 25 years ago I visited a telecom switch center in Paris, the one under the Tuileries garden next to the Louvre. They had a huge and empty diesel generators room. They had all been replaced by a small turbine (not sure it's the right English term), just the same as what's used to power an helicopter. It was in a relatively small soundproof box, with a special vent for the exhaust, kind of lost on the side of a huge underground room.
As the guy in charge explained to us, it was much more compact and convenient. The big risk was in getting it started, this was the tricky part. Once started it was extremely reliable.
> Edit: I bet it had diesel generators when it was in service with AT&T to boot.
That's where AT&T screwed up in Nashville when their DC got bombed. They relied on natural gas generators for their electrical backup. No diesel tank farm. Big fire = fire department shuts down natural gas as wide as deemed necessary and everything slowly dies as the UPS batteries die.
They also didn't have roll-up generator electrical feed points, so they had to figure out how to wire those up once they could get access again, delaying recovery.
I've seen some power outages in california, and noticed that comcast/xfinity had these generator trailers rolled up next to telephone poles, probably powering the low voltage network infrastructure below the power lines.
Edit: I bet it had diesel generators when it was in service with AT&T to boot.