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

George Michaelson ggm at algebras.org
Wed Sep 27 09:32:23 AEST 2023

It may be obvious, certainly to anyone who owns the BSTL series (I
don't. I read it in the library at uni), but would I be  right in
thinking the motivation behind "real time UNIX" was switching? It's
the closest problem to Bell labs which demands time critical outcomes,
the delay tolerance in circuit establishment and end-to-end telephony
signaling was there, but it was finite. And, for capacity planning
purposes being told a single unit of UNIX logic controlling a
telephone switch could handle X call setup and tear-down events per
second meant you could do the Erlang sums over customers call volumes
and phone handset counts.

The british digital switch experience in the System-X series Was
GEC/Plessey, and ran CORAL which was the real time system they used to
do MILSPEC stuff. It was explicitly fault tolerant design, lots of 2
and triple redundant componentry.


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