Page "CompuServe" Paragraph 6

Later, the central multiplexers in Columbus were replaced with PDP-8 minicomputers, and the PDP-8s were connected to a DEC PDP-15 minicomputer that acted as switches so a phone number was not tied to a particular destination host.

Finally, CompuServe developed its own packet switching network, implemented on DEC PDP-11 minicomputers acting as network nodes that were installed throughout the US ( and later, in other countries ) and interconnected.

Over time, the CompuServe network evolved into a sophisticated multi-tiered network incorporating Asynchronous Transfer Mode, Frame relay, Internet Protocol and X. 25 technologies.