[TELECOM Digest Editor's Note: I know from my personal experience that
> Illinois Bell had ESS in the Wabash office in downtown Chicago in
> 1974, along with the Superior office on the near north side the same
> year. But I think they were just the first editions or versions of
> that type of switch. PAT]
The Western Electric #1ESS was invented in 1965, with the upgrade #1AESS invented in 1976. These were analog switches with computer control (and in my opinion, glorified crossbar switches with reed relays).
Others, as I've mentioned before, came out with their fully digital switches before Western Electric came out with their fully digital end office switch (the #5 ESS) in 1982.
Dave Perrussel Webmaster - Telephone World
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