out-of-mainstream minis

Sean Caron scaron at umich.edu
Fri Jul 3 12:48:29 CDT 2015

I was going to write almost exactly this ... although the Wiki page
mentions that AT&T was one of the primary customers of the System/7, AFAIK,
the common control on the 1/2/3/4ESS switches was a proprietary WECo design
that was highly integrated into the design of the switch itself ... in the
5E, I think the common control became a 3B20D mini and later this was
replaced with an emulator of same running on some number of SPARCstations

For operations support systems, I thought DEC was very popular in the Bell
System; I thought many OSS ran on some modified UNIX variant or another on
PDP-11 or, perhaps later, VAX which would have roughly been contemporaneous
with the System/7 ... I would be really interested to know what the
System/7 did at AT&T if anyone is familiar.

I have a particular interested in collecting digital telephone switches ...
and I too find it a real bummer that we could find ourselves in a world
where there isn't one complete, functional example of such historic
machines as the 1AESS, 4ESS, DMS-100, 5ESS and so on. Many completely
functional examples of the old cord-boards and even the electromechanical
step-by-step and crossbar switches exist in private hands but as far as I
know, nobody has managed to save a complete digital CO switch of any



On Thu, Jul 2, 2015 at 11:33 PM, Christian Gauger-Cosgrove <
captainkirk359 at gmail.com> wrote:

> On 2 July 2015 at 17:39, Mike Ross <tmfdmike at gmail.com> wrote:
> > Take the IBM System/7. Successor to the 1800, succeeded by the
> > Series/1. They were *ubiquitous* - one in every telephone exchange in
> > the USA, I've heard. They even made a special ruggedised version for
> Being into telephony, I can say that I've not heard anything about IBM
> System/7 machines being used in exchanges. I do know that the WECo ESS
> exchanges did, of course, have computers. But the ESS exchange
> computers were custom systems and architectures built by Western
> Electric.
> The 1ESS/1AESS computer architecture is however, nearly completely
> extinct. There are, I believe, only two 1ESS/1AESS switches left. One
> is a partial, and non-functional exchange at the museum of
> communications in Seattle; the processor is complete, and it has one
> of each requisite switching frame, but it can't be used as they need
> to recompile the software that runs it (which isn't possible as
> they're lacking the crucial internal compiler that ran on WECo's IBM
> System/3x0 machines). The other 1ESS/1AESS switch is a complete and
> functional unit, still in service, last I heard. But there are plans
> to scrap it and put in a modern switch in its place. Saving it would
> be a difficult proposition, to say the least.
> Regards,
> Christian
> --
> Christian M. Gauger-Cosgrove
> Contact information available upon request.

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