Path: utzoo!attcan!uunet!pilchuck!ssc!markz
From: markz@ssc.UUCP (Mark Zenier)
Newsgroups: sci.electronics
Subject: Re: COMPOSITE -> TTL
Keywords: TTL, COMPOSITE, connect, etc.
Message-ID: <748@ssc.UUCP>
Date: 24 May 90 18:07:50 GMT
References: <24431@unix.cis.pitt.edu>
Distribution: all
Organization: SSC, Inc., Seattle, WA
Lines: 44

In article <24431@unix.cis.pitt.edu>, fmgst@unix.cis.pitt.edu (Filip Gieszczykiewicz) writes:
> 	Greetings. I have a VCR with a COMPOSITE output that I
> 	want to use. I also have a _large_ number of terminals
> 	that lack the "digital" sections but have the CRT drive
> 	circuits in "prime" condition. Is it possible to use
> 	it with COMPOSITE? How? Specifically, I have a couple
> 	Visual 90s and some Televideo 912Cs that I would like to
> 	make something of... Anyone done it before?

Here's the pinout that seems to be standard for open frame TTL drive monitors.

01 ground          
02 contrast pot, one end (50k ohm ?)
03 contrast pot, the other end
04 contrast pot, wiper
05 ground          
06 horiz sync or drive       
07 + power (12 or 15 volts)         
08 video        
09 vert sync or drive       
10 ground          

TTL levels or something like them on 6, 8, and 9.

The connector's I've seen are either 10 pin .156 inch card edge or
a 10 pin .1 molex header (single line).

Here are some caveats:

1.  If it's a high volume product, they may not have bothered following
with this connector.

2. The video is very nonlinear, and inverted from the normal composite video.
    0 volts = dark, TTL 1 = bright.

3. Sync must be provided, if you want interlace, you have to get the vertical
timing just right.  Even worse, some units don't have oscillators built in, 
and the inputs are drive signals with frequency and pulse width requirements.
Get these wrong and the Horizontal Sweep circuit goes up in smoke.

4. You'll probably have to trap out the color subcarrier and sound.  Most
of these monitors are good for 8 to 12 Mhz.

Markz@ssc.uucp