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From: sandersr@ecn-pc.UUCP (Robert C Sanders)
Newsgroups: net.micro.pc
Subject: Re: RGB to Composite video converter
Message-ID: <524@ecn-pc.UUCP>
Date: Fri, 27-Jun-86 00:27:29 EDT
Article-I.D.: ecn-pc.524
Posted: Fri Jun 27 00:27:29 1986
Date-Received: Mon, 30-Jun-86 03:16:21 EDT
References: <193@ranhome.UUCP>
Reply-To: sandersr@ecn-pc.UUCP (Robert C Sanders)
Organization: Electrical Engineering Department , Purdue University
Lines: 44
Summary: Where to get one; AT&T Truevision

In article <193@ranhome.UUCP> randy@ranhome.UUCP (Randy Horton) writes:
>
>I remember once seeing advertised somewhere a converter which would convert
>RGB video to composite video.  ...  However, now I have a compatible with a
>color graphics card.  It has a composite video jack, but only monochrome comes
>out of it.  I would like to use this machine with my composite color monitor
>in color.
>
>If anyone out there knows anything about where I might be able to get a RGB to
>composite adaptor, I would much appreciate hearing about it.
>

I know of the exact board that you are looking for:  it is the "Truevision
   Composite Video Adaptor", made by AT&T, Computer Systems Group, Indianapolis
   Indiana.  This adaptor was designed for AT&T's TARGA series video boards,
   can also act as a stand-alone unit.  It has external connectors for:
   RGB input; NTSC generating RS170A Color Composite video output; NTSC Color
   Composite (RS170A) input; generating RGB output.  It plugs into any IBM
   PC compatible, and has software included that can set the saturation,
   various hues, brightness, and contrast.

NOTE!!! The RGB output of most computer video boards is IBM-standard TTL RGB
   (or really psuedo-RGB) at 0 to ~3.8 volts, with separate vertical sych,
   and hori-sync, and intensity lines.  Analog RGB, or broadcast RGB,
   uses 4 pins -- composite sync, and the three colors at 0 to .714 volts.
   To use the board with a standard TTL RGB board, you will have to use
   resistor networks to pad the voltage levels down, and a NOR gate to
   generate negative-going composite sync from H-sync and V-sync, and with
   a pad to bring the voltage down.  Lastly, in your resistor pads, use a
   resistive summer to add the different intensity lines; you could even
   use high-frequency OP amps as adders, running at 6 MHz or so.

The board goes for $495 from AT&T computer distributors.

					- bob
-- 
------------
Continuing Engineering Education Telecommunications
Purdue University

"Time is a mouse that requires constant feeding..." -- me

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