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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!qantel!hplabs!tektronix!tekcrl!tekgvs!peterh
From: peterh@tekgvs.UUCP (Peter Hildebrandt)
Newsgroups: net.micro.amiga,net.micro,net.micro.apple
Subject: Re: Amiga monitor
Message-ID: <1207@tekgvs.UUCP>
Date: Thu, 5-Sep-85 21:00:31 EDT
Article-I.D.: tekgvs.1207
Posted: Thu Sep  5 21:00:31 1985
Date-Received: Sun, 8-Sep-85 16:40:30 EDT
References: <1204@tekgvs.UUCP> <577@sftig.UUCP>
Reply-To: peterh@tekgvs.UUCP (Peter Hildebrandt)
Organization: Tektronix, Beaverton OR
Lines: 30
Xref: watmath net.micro.amiga:75 net.micro:11863 net.micro.apple:2123
Summary: Answers to the RGB / RGBI question 

In article <577@sftig.UUCP> rbt@sftig.UUCP (R.Thomas) writes:
>What is the difference between RGBI digital,
>RGB analog, and NTSC composite, and all the rest.  (The Apple RGB Color
>card produces something called XRGB, what's that?)
>
>Thanks for any light you can shed!
>
>Rick Thomas
>ihnp4!attunix!rbt

TTL or RGB digital refers to a video source of three signals, RED, GREEN,
and BLUE, each of which has a digital signal level (0 or 5 Volts).  RGBI
digital adds a fourth bit, INTENSITY, which is also a digital signal.
Hence, RGB digital gives eight colors, whereas RGBI digital produces 16.

RGB analog is also a video source consisting of three signals, RED, GREEN,
and BLUE, but in this case, the signals are analog voltages from 0 to 1 volt.
With analog RGB, you can theoretically get an infinite number of colors on 
the screen, but most analog systems are limited by the size of the digital
to analog converter inside.  

NTSC composite is standard composite video, combining the red, green, and
blue signals into one.  Most video cassette recorders output NTSC composite.
NTSC video is usually output through a RCA phono jack on microcomputers.

Generally, the signal quality is degraded when the signals are combined for
NTSC video, and therefore, any kind of RGB is preferable.

			Peter Hildebrandt
			Tektronix Laboratories