[TUHS] Known Specimens of Pre-5ESS UNIX Telephone Switching Software?

Kevin Bowling kevin.bowling at kev009.com
Tue Sep 26 12:20:54 AEST 2023

On Mon, Sep 25, 2023 at 6:25 PM segaloco via TUHS <tuhs at tuhs.org> wrote:

> Hello, my studies lately bring me to the question: Are there any extant
> examples of telephone switching software, built on UNIX, from the various
> parts of the Bell System prior to the introduction of the 5ESS and 3B20D?
> My focus veers earlier as some 5ESS/3B20D/DMERT technology is still in
> active use, that sleeping dragon can lie.

Your best bet may be to contact Sarah Autumn at the Connections Museum,
they have a 1ESS and 3ESS.

I don't remember if they have the 1A variant but they should have the BSPs
for all of this which would give you a lot of what you are after.

> What's gotten me curious is reading about 1ESS in a BSTJ volume I picked
> up, noting the particulars on how previous concerns of manual and
> electro-mechanical systems were abstracted into software.  Even without
> surviving examples, were previous systems such as the 1ESS central control
> ever ported to or considered for porting to UNIX, or was the hardware
> interface to the telco lines too specific to consider a future swap-out
> with, say, a PDP11 running arbitrary software?  Columbus's SCCS (switching,
> not source code) also comes to mind, although all I know that survives of
> that is the CB-UNIX 2.3 manual descriptions of bits and pieces.
> By the way, it's funny, I have UNIX to thank for my current experiments
> with telephones and other signalling stuff, what with making me study the
> Bell System more generally.  It's starting to come full circle in that I
> want to take a crack at reading dialing, at least pulse, into some sort of
> software abstraction on a SBC that can, among other things, provide a
> switching service on top of a UNIX-like kernel.  I don't know what I'd do
> with such a thing other than assign work conference call rooms their own
> phone numbers to dial with a telephone on a serial line...but if I can even
> get that far I'd call it a success.  One less dependency on the mobile...
> - Matt G.
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