I picked up a bunch of Black Box "Short Haul Modems" yesterday.
I hadn't ever looked at such things closely before, but they
are just powered RS-232 to current loop converters.
Very handy for old CPUs that only have current-loop TTY
interfaces, like the Varian 620, or hooking a 33 to modern
gear (assuming it can talk 110 baud).
I'll get the circuit traced out in the next few days, and
check what current they are running through the loop.
Has anyone got one? I don't see it on bitsavers and oddly enough
Teletype Corporation isn't in the vendor drop-down list on manx!
--
"The Direct3D Graphics Pipeline"-- code samples, sample chapter, FAQ:
<http://www.xmission.com/~legalize/book/>
Pilgrimage: Utah's annual demoparty
<http://pilgrimage.scene.org>
"John K." <john3000 at cox.net> wrote:
> Going way beyond the "Party Line" topic, does anyone remember the Sytek
> system? The Sytek network used bidirectional CATV technology for the
> backbone and network interfaces that used two Z80 processors to connect
> RS-232 devices. One Z80 handled the RS-232 interfaces (you could have 1 >
to 8 19,200 bps RS-232 ports) and the other handled the
> modulation/demodulation of the RF carrier. A 68000 Unix box acted as
> the network control center (NCC). When you turned on a terminal and hit
> return you got the attention of the NCC and it gave you a menu of
> available devices (ones which you had permission to access ANDed with
> the devices [systems] which had available ports). I know the Sytek
> system was used at NASA, as it was through NASA that we found out about >
the Sytek "local area network" equipment sometime about 1979 or 1980.
> With the CATV bandwidth and the frequency spectrum divided up for
> various uses, the Sytek network allowed a dozen or so video channels, a
> few thousand phone calls, and several thousand 19.2 kbps terminal
> connections simultaneously on a single cable. Not bad for late 1970's
> technology.
>
> John
(Sorry for the late response...)
Thank you for bringing up that topic! The whole concept was called
"LocalNet" back when it ruled, right? Over the course of time, about ten of
the two-port desktop units ("T-Box" 2502) and four or so of the 32-port
rackmount boxes ("S-Mux" 2532) found their way to the University computer
museum of Erlangen University where I work. I've heard there once were lots
more of them used here for timesharing the computing center machines form
terminals scattered all around the campus.
We're toying with the idea of setting up a small segment of CATV cable (we
still have some old Magnavox line amplifiers, splitter jacks and such), but
we seem to miss a crucial piece of hardware: the bootloader box, from which
the "modems" receive their firmware and channel assignments and without
which they consequently won't work. We suspect it was junked together with
the main stock of modems about ten years ago.
I've not been able to find much about LocalNet online, so I don't know what
type designation the bootloader box has, what it looks like and so on. Since
it is most important for the functional demonstration network we'd like to
have, I'd be very thankful for any information.
Yours sincerely,
--
Arno Kletzander
Stud. Hilfskraft Informatik Sammlung Erlangen
www.iser.uni-erlangen.de
"Feel free" - 10 GB Mailbox, 100 FreeSMS/Monat ...
Jetzt GMX TopMail testen: http://www.gmx.net/de/go/topmail
Hey, I was just skimming Knuth's Art of Computer Programming chapter
where he talks about external sorting. It occurred to me that doing a
massive external sort would be an impressive demo for someone viewing
a collection.
Does anyone here own enough 9-track magtape drives to do external
sorting and multi-tape merge operations? It would be cool to watch a
time-lapse film of the operation!
--
"The Direct3D Graphics Pipeline"-- code samples, sample chapter, FAQ:
<http://www.xmission.com/~legalize/book/>
Pilgrimage: Utah's annual demoparty
<http://pilgrimage.scene.org>
Posted to a DFW area news group. Wish it were close to me!
-------- Original Message --------
Subject: Free HP Computers and Monitors (Plano)
Date: 10 Apr 2006 06:47:21 -0700
From: funkychateau <funkychateau at yahoo.com>
Organization: http://groups.google.com
Newsgroups: dfw.forsale
Free: Four HP 9836 computers and two companion monitors. Great if you
have test equipment with HPIB/GPIB interface and need a BASIC
controller. 972-517-4900
well, sort of
http://www.barrcentral.com/support/documents/manuals/3270%20for%20RJE%
2094%20Manual.pdf
Is a product manual for a DOS product that could simulate the
establishment controller
and the terminal, so it has a nice overview of the whole path back to
the mainframe.
It was enough to answer most of my questions about where to look for
more detailed
information if I ever need to know..
