[TUHS] Joe Condon [ long, slightly off-topic post ]

Jon Steinhart jon at fourwinds.com
Sun Apr 21 08:57:27 AEST 2019

So as part of my attempt to remember the names of the folks with who I worked
I just read Joe's wikipedia page which doesn't seem accurate to me.  If this
is too off topic let me know.

The page says that Joe "was exposed to UNIX on the Honeywell 516 machines in
the early 1970s."  This seems wrong to me.  We did have a 516, but it ran an
experimental virtual memory system called 516-TSS.  I lived on this system
and still have some of the octal instruction opcodes burned into my brain-ROM.
I seem to recall that the department got a PDP-11/40 that ran UNIX version 3 in
maybe the summer of 1972 which I used for writing up the documentation for my

The page also says that "Condon and Ken Thompson promoted the use of the C
programming language for AT&T’s switching system control programs.  Condon
acquired a small AT&T PBX (telephone switch) that handled about 50 phones;
he made the necessary hardware changes and Thompson wrote the necessary software
programs. The PBX code rewrite in C was a success and hastened the adoption of
C for all switching system software within AT&T."  This also doesn't match my

One of the big projects in the department was what I think was called SS1 for
Slave Switch 1, which was an all-digital telephone exchange.  It replaced some
other monstrosity whose details I can't recall except that Joe and Dave Weller
signed the appropriate paperwork allowing me to take a good portion of it home
when it was decommissioned giving me a huge stock of Augat wirewrap boards and
7400-series parts.  The SS1 was originally going to use LSI-11s but the stupid
way in which DEC implemented the DRAM refresh made that impossible.  I think
that the final thing used a couple of PDP-10s.  As part of being all-digital
it used the digital filter work by Jim Kaiser and Hal Alles.  I do remember
going into Carl Christensen's office to ask him a question and found him staring
at a huge C listing; it turns out that a bug in the code had caused SS1 to send
KP pulses without their corresponding ST pulses with the result that every single
keypulse sender in the Berkeley Heights telephone exchange was taken off line and
needed to be manually reset to restore long distance service.  They were not happy.

Anyway, unless there was something that happened later after I was gone, I'm
thinking that the wikipedia page is incorrect and that this PBX was built, not
acquired.  It was, as far as I know, the first use of C to control machinery.

It's actually because of this machine that I'm trying to track down the name
of some folks from down at the end of the hall.  I have strong memories of the
Bell System exhibit at the '64 World's Fair, especially the booth where one
could go and talk and they had bar graphs on a monitor showing the spectrum
of your speech and could mess with it.  Many years later, while waiting for
some deck of cards to finish loading, I poked my head into the lab down the
hall to see what they were doing in there, and noticed polaroid photos of that
exhibit featuring the guys in the lab.  Once they stopped telling stories from
the World's Fair, they taught me a lesson about systems engineering that opened
my eyes.  They were developing a circuit that replaced the pound of iron hybrid
transformers that were on every telephone line with a small toroid and an op-amp.
Their circuit would sense when the iron was getting close to saturation and run
current through an additional winding to keep it in the linear region.  While
that circuit cost a lot more than a hybrid transformer, it paid for itself by
reducing the amount of concrete needed to build telephone exchanges.

Would love to know who these guys were which is why an org chart would help.
And maybe someone out there like Ken can help me out with the accurate history.


More information about the TUHS mailing list