TI-99/4A Comments

From: Philip.Belben_at_powertech.co.uk <(Philip.Belben_at_powertech.co.uk)>
Date: Fri Jun 13 09:15:08 1997

> > if anyone can shed some light on these, let us know):
> >
> > 1. "12v vid"
> > 2. R-Y (colorburst clock)
> Red - (minus) Yellow
> > >3. Audio out
> > >4. Y
> Yellow
> > >5. B-Y (ext video input?)
> Blue - yellow
> > >U. Ground
> Just a different way to send an 'RGB' signal. I'm not sure what the merit is
> of sending it this way... any video techs out there? I'll cc this to one who
> might know.

Um... No. Sorry. Close though.

Y is not yellow, i'm afraid. These signals derive from the way
luminance and chrominance are handled in a telly.

Y is intensity (luminance). It is made up of red, green and blue in the
rough proportions that generate intensity in a human eye. This is the
only part of the signal that a black and white telly (or greyscale
monitor) would decode.

The other two signals are the quadrature components of chrominance.
They are derived from Y by subtracting red and blue, and are normally
called U and V (in some order).

The colour telly receives U and V phase modulated onto a subcarrier (I
think). The hue control on American tellies sets the baseline against
which phase is measured here. (In Europe, the PAL system reverses the
phase each line, so any hue errors should cancel out)

The signals are transmitted this way in broadcast TV to ensure
compatibility between colour and BW tellies. They are also the signals
that would normally be sent to a TV (UHF or VHF) modulator from the
computer, hence their presence on the video connector.

Hope this helps! I could be more specific if I had some of my reference
books from home...


<><><><><><><><><><><><><><> Philip Belben <><><><><><><><><><><><><><>
      Bloedem Volke unverstaendlich treiben wir des Lebens Spiel.
      Grade das, was unabwendlich fruchtet unserm Spott als Ziel.
      Magst es Kinder-Rache nennen an des Daseins tiefem Ernst;
      Wirst das Leben besser kennen, wenn du uns verstehen lernst.

Poem by Christian Morgenstern - Message by Philip.Belben_at_powertech.co.uk
Received on Fri Jun 13 1997 - 09:15:08 BST

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