Re: Non-Bell ESS?

[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 No. 1ESS (replaced early on by the 1AESS) was well along in deployment by 1974. The first installation in California was in Beverly Hills in 1967. That wasn't long after the first installation somewhere in the east, perhaps 1965?

The difference between the 1 and the 1A was larger volitile memory (call control storage) and giant disk drives for program control storage. Many Bell LECs upgraded their existing 1ESS switches to 1As once deployment of the 1A began.

Once the digital 5ESS came along, the regional Bells had already aquired a preference for Nortel's DMS-100, mostly because it was cheaper and would do an adequate job in all but the most intensive urban environments (the 5ESS was definately better, but perhaps a Lexius when a Ford would do. ;-)