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From: tgg@otter.hpl.hp.com (Tom Gardner)
Newsgroups: sci.electronics
Subject: Re: Hues
Message-ID: <1770026@otter.hpl.hp.com>
Date: 11 Dec 90 16:31:51 GMT
References: <2401@ecrc.de>
Organization: Hewlett-Packard Laboratories, Bristol, UK.
Lines: 17

From possibly incorrect memory:

	- the transmission path between the transmitting and receiving 
	aerials can introduce phase distortions

	- in the NTSC system these distortions appear as changes in hue

	- in the PAL (Phase Alternation Line) system the distortion between
	two successive lines is cancelled by adding the complement of one
	line to the next. This converts the changes in hue into changes in
	saturation. 

	- this is an improvement because the eye is less sensitive to changes
	in intensity than to changes in hue

The PAL system is fully compatible with the preceding monochrome systems.
The major extra component required for a PAL set is a 64us delay line.