AT&T Long Distance Network

 

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.

AT&T Long Lines History

Introduction of Direct Distance Dialing (DDD)

Old AT&T/Bell System Operator Routing Codes

AT&T Historical Videos

AT&T Tandems

The switching systems that connected central offices to and from the “Long Distance” network were the many crossbar (and later digital) tandem switching systems.

AT&T 4A Crossbar Tandem List (historical)

AT&T 4ESS Tandem List (current)