What composes the AT&T Long Distance network? The switching systems that connected central offices together, and the transmission systems that connected the switching systems together. This section discusses both the Class 4 tandem switches as well as the transmission systems including microwave and coaxial cable.
AT&T Long Lines
AT&T’s Long Lines Network is the backbone of what we called “Long Distance” for many years. This encompass the microwave and coaxial cable transmission systems that sent long distance calls between Points A and B for many years.
The switching systems that connected central offices to and from the “Long Distance” network were the many crossbar (and later digital) tandem switching systems.
More AT&T History
Even more history can be found here!