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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 15th Jan 2021, 9:03 pm   #1
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 490
Default 875 Line

OK, not a mistake, I really mean 875 line.

All this talk of 819 lines has made me think of my days in the 80s working on the design of 875 Line, 60 Field Interlace 4:3 aspect ratio colour systems for flight simulators.

It wasn't a one-off situation, this was a global standard defined as NATO standard STANAG 3350 alongside what could loosely be described as 625/50 PAL and 525/60 NTSC.


Our Image Generator systems (a sort of hybrid analogue/digital real-time picture source) fed 26" shadowmask colour monitors mounted in all glass collimators giving an image seemingly originating from 15 Metres away.

There were many other military/civil systems using 875 Line, but does anything survive? I have a brand new 26" high resolution RCA colour CRT but that's all. There were monochrome vidicon cameras, digital sources, flying spot scanners and all sorts of wonderous display systems. I have never seen anything for decades - has it all gone to the scrappers?

Anybody else here work with 875/60?

Just a thought!

Best regards,

Paul M
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Old 15th Jan 2021, 9:16 pm   #2
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Join Date: Apr 2012
Location: Wiltshire, UK.
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Default Re: 875 Line

I remember back in the early-1980s I did some stuff for an early ~~Geographic Information System~~ [well, that was what the client called it, we were subject to COCOM export-controls] involving NASA-supplied satellite-imagery, a GEC4090A minicomputer and a bunch of rather-large CRT displays made by a company which was either SIGMA or SIGMEX. These displays had a whole slew of odd resolutions; they started-up working as rather-mundane DEC VT320-emulation mode so you could log-in but then the software sent the necessary codes to switch to graphics-mode - and the mouse started to work!

875 was one of the selectable resolutions, along with 1010??

Big problem we had was when the software crashed - and did its inevitable dump-in-VT320-mode, which was of course utter garbage to the display that was still in hi-res video-mode. I wrote a sort-of 'shim' program in the odd GEC4000-seriies BABBAGE high-level-assembler that trapped the panic-semaphore and issued the "Switch back to VT320-mode" commands so the dumps could be read.
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