cctech digest, Vol 1 #379 - 30 msgs

From: William Donzelli <>
Date: Fri Feb 21 17:22:00 2003

> 22. Simplex.jpg. This console provided operation and maintenance of the Long
> Range Inputs and Outputs. Simplex because there was no redundant hardware.
> Each radar station fed digitized data to the DC over public telephone lines (a
> first - they had to invent the modem!). The DC also sent data to the
> neighboring DCs and to the Command Center (the AN-FSQ-8 computer).
> From the text, this system was already in operation back in 1962, or earlier.
> It claims that here a modem was designed for the purpose of it. Does anyone
> know more on this? Who was the manufacturer? When started up, and shut down?

The radar video datalinks for SAGE were digital, and they did work over
standard landlines, but they were real time - not file transmissions.
Pure streaming digitized radar video, warts and all, as the radars sent
whatever they saw, including noise. There was no real protocol, just some
crude timing information.

There was no "modem", just a "mo" and a "dem". One half did the
transmitting (AN/FST-1 - these were typically at the radar sites), and
another half did the receiving (AN/FSR-1, I think - typically at the
computer ends). Sometimes, when gap filler radars were used, a whole bunch
of AN/FSR-1s would be located with one AN/FST-1 and something called an
AN/FSA-10. This latter unit would merge the incoming video data streams
together, and relay the merged data.

SAGE did have some "real" digital data transmissions - typically to the
aircraft fitted with something called an AN/ARR-39. This system allowed
SAGE to "fly" the aircraft (the pilot still did all the work, but was
relieved of thinking. The complete control of aircraft by SAGE without
pilot interaction was planned for, but "never" happened). The protocol is
quite simple, and works on subcarriers of the standard tactical UHF band.
Full AN/ARR-39s are quite interesting - four boxes, weighing only a little
he over 100 pounds, with several hundred tubes and over 500 relays.

William Donzelli
Received on Fri Feb 21 2003 - 17:22:00 GMT

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