From mboxrd@z Thu Jan  1 00:00:00 1970
From: doug@cs.dartmouth.edu (Doug McIlroy)
Date: Tue, 28 Feb 2017 16:12:45 -0500
Subject: [TUHS] Was 5ESS built on UNIX?
Message-ID: <201702282112.v1SLCjcp015051@coolidge.cs.Dartmouth.EDU>

As Corey said, administrative computers in switching centers
ran Unix, but the call-processing machines ran an unrelated
operating system. The Unix lab did influence that operating
system. Bob Morris instigated, and Joe Condon, Lee McMahon,
Ken Thompson and others built TPC (the phone company), a switching
system controlled by a PDP-11. This system actually ran the
phones in CS Research for several years. ESS5 adopted some
of TPC's architecture, though none of its code.

Doug