The following article is from "Hardware -- `Tips and Tricks'" version 95.04.28 and I got permission from the author to put this on my pages also.

`True' VGA Grey-Scale

Added on April 21, 1995

Let's say your BBS computer has a monochrome VGA monitor attached to it. Back in the DOS days, in text mode, this wasn't such a big problem. Nowadays, some people are running OS/2 or Windows in VGA mode. In graphical sessions, some colours are invisible. Apparently, monochrome monitors read only one of the RGB pins. It doesn't take more then 3 resistors to convert a colour signal to a decent grayscale signal however ... and here's the way to do it:

[Editor's note: the following is an explanation of a rather interesting ASCII picture which is, unfortunately, not reproducible on the web without going into inlined graphics which this author is not very good at <grin>]

Use a 180-ohm resistor between the R pin and ground.
Use an 82-ohm resistor between the R pin and the video on the monitor.
Use a 22-ohm resistor between the G pin and the video.
Use a 240-ohm resistor between the B pin and the video.
Use a 100-ohm resistor between the B pin and ground. 

All resistor values are in ohms. The video signal in the original wiring is taken from the green signal. Connect this resistor network between the plug and the video wire, and leave the other wires on the VGA plug the way they were. (On the VGA plug, pin 1 is red, pin 2 is green and pin 3 is blue.)

* Kees Stravers - [email protected]

Circuit diagram as an ASCII picture

                        ____
 RED   1 >-+-----------|____|----+
           |  ____     82 ohm    |
           +-|____|-+            |
            180 ohm |            |
 BGND  6 -----------+            |
                        ____     |
GREEN  2 >-------------|____|----+-------------> VIDEO OUT
                       22 ohm    |
                        ____     |
 BLUE  3 >-+-----------|____|----+
           |  ____     240 ohm   
           +-|____|-+            
            100 ohm |            
 BGND  8 -----------+