For that matter... why make the modulator at all?!? If
the IIc
has composite video, why bother with an RGB to composite?
Sounds like a build-your-own macTV for people who want to
use their own TV/monitor for the computer. I have one of these
boxes for VGA->NTSC... they're inexpensive now. An RGB to
NTSC converter may more properly be called a "scan converter",
"modulator" is typically the name given to NTSC -> RF over coax.
You can use a scan converter And a modulator together
ComputerRGB -(scan converter)-> NTSC -(modulator)-> TV.
John A.