I read about it in Exploding the Phone: The Untold Story of the Teenagers and Outlaws who Hacked Ma Bell by Phil Lapsley

Many more BSPs can be found here at The Telecom Archive

I’ll have to show my coworkers this. We now have contractors clean our buildings

My dad started as a sweeper in a long distance switching office in 1954. He told me that they were incredibly strict on the process because dust that became airborne would be picked up by the fans and could then get into the mechanical relays. I remember walking through the 24' high racks of mechanical switches as a kid, whole floors of nothing but racks.

99.999% uptime.

I don’t think they have moved on much - they were an appalling vendor to deal with - they supplied all of our regional MPLS. Lead times for any new connections sometimes went into years where others could (and now thankfully do) in just a few weeks. Our reps were constantly on PTO, and we had an outage that lasted a week (due to failed hardware on a very old piece of infrastructure).

Abysmal to deal with. Glad I have nothing to do with them any more

I work at mines and had to get signed off on how to correctly shovel and throw salt during the winter.

My dad worked in a facility like that. Holy crap, the smell... ozone, coffee, and cigarettes, nothing like it (yeah, smoking was allowed, it wasn't a Bell facility). I doubt I'll ever smell that again.

Colorado school of mines?

Nah labourer at minesites in the nickel capitol of the world

Norilsk?

For those that don’t know what mechanical relays mean for telephones:

https://youtu.be/bvPH-tsD9ZM

Very nice. I saw equipment like this in an old local exchange on a tour. My dad's 4A office looked a bit like the 1960's "country office" inset.