If you're into vintage telephone network sounds (and some really excellent technical descriptions of phone phreaking) take some time to listen to Evan Doorbell's recordings: https://www.evan-doorbell.com/
I grew up in the tail end of analog switches near my home. I remember the sounds of making phone calls changing over a few years. They became a lot less interesting and a lot more uniform. The sounds you'd hear calling the bigger towns in the area slowly took over the sounds you'd hear when calling smaller towns or out into the country.
I really appreciate the work that he's done with documenting and narrating his tapes and curating the work of others. I've learned so much about the telephone network of yore from his recordings and, very specifically, about the sounds of the network that I remember from my youth. (I also get a big kick out of Dom Tuffy...)
I grew up in the tail end of analog switches near my home. I remember the sounds of making phone calls changing over a few years. They became a lot less interesting and a lot more uniform. The sounds you'd hear calling the bigger towns in the area slowly took over the sounds you'd hear when calling smaller towns or out into the country.