Around the turn of the century, I installed high speed switches for dsl at central offices. In Louisiana they had some ancient machines in there that connected the calls at all the pay phones connected to that office. A central office covers about four square miles around it. You’d be surprised how often one of those old mechanical switches moved to connect a call. They were referred to as “quarter machines” because that sound meant somebody dropped one in a phone. They were still using those decades old things because they were stone reliable.