In <965720245.328301@inv.ihug.co.nz>, "Roger Johnstone" writes: > >---------- >In article <5iFj5.3254$aK5.53940@news1.online.no>, "Deacon Blue" > wrote: > > >>Hi! >> >>How is the RGB signal on the Apple III defined? Analog RGB as on the IIGS, >>or a digital Video-7 RGB signal? Any update on this appreciated! >> >>best regards > >It's digital RGB. Apple described it as XRGB, it is not the same as the RGBI >(red, green, blue, intensity) that the IBM PC CGA cards used. I think the >Video 7 produces a CGA-compatible RGBI. I think with XRGB it was just a >4-bit code which was used to pick one of 16 colours rather than a real RGB >signal. Um, I think. > You are correct about everything except the the last part. Apple actually defined XRGB as analog RGB, even though it consisted of 4 digital outputs. These digital outputs could be run through a simple circuit (Apple called it a "summing network") which supposedly produced analog RGB. The AppleColor Monitor 100 has this circuitry built in. There is a diagram on how to build this circuit in the Apple III manual, which will allow the use of a "normal" analog RGB monitor. And, as noted in another post, somewhat coincidentally, an Apple IIGS monitor will produce a picture from the XRGB signal, but the colors will be wrong and you will only get 8 colors (instead of 16). Louis PS If anyone has an AppleColor 100 monitor they want to sell, please let me know.