Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!bbn!ginosko!cg-atla!welch
From: welch@cg-atla.UUCP (John Welch)
Newsgroups: sci.electronics
Subject: Re: NTSC-PAL (in)compatibility
Message-ID: <7263@cg-atla.UUCP>
Date: 21 Jun 89 17:00:37 GMT
References: <124@nisca.ircc.ohio-state.edu> <566@axis.fr>
Reply-To: welch@cg-atla.UUCP (John Welch)
Organization: Agfa Compugraphic Division
Lines: 29


Just off the top of my head, the main difference between SECAM and PAL
is the way in which color information is processed on each line.

Roughly, SECAM stands for Systeme Electronique Couleur Avec Memoire.
Or, Sequential Color with Memory, not a direct translation, but it
gives a good description of what happens in a SECAM system. 

In a SECAM system, the red and blue color difference signals are
transmitted on alternate lines. This requires a one scan line memory to
decode for green.

In PAL, or Phase Alternation ,or alternating, Line, one of the subcarrier phasesderived from the color burst is inverted in phase from one line to the
next. This is done to minimize errors in hue which may occur during
color transmission.

These systems are both 625 line 50 Hz, which is why Black and White
signals would work. The only difference in the two is how they encode
color.

Remember, NTSC = Never The Same Color :-)

This info was culled from the Raster Graphics Handbook put out by
Conrac.
-- 
John Welch                            | "Why should YOU care what other
Agfa Compugraphic Division            |         people think?"
Wilmington Ma 01824                   | 
{ulowell|decvax|cgeuro}!cg-atla!welch |        Richard Feynman