LocalNet (was: "party line" for terminals?)

Arno Kletzander Arno_1983 at gmx.de
Tue Apr 11 05:04:44 CDT 2006

"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

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