NOTE: This comes as a DIY kit for you to solder together. It does not come assembled like in the photos. The photos show the completed item. Current PCB stock is white, not green.

This device attaches to the standard feature connector of an EGA card (such as an original IBM EGA card), and provides a monochrome composite video output on a 4-pin header, useful for IBM 5155 internal CRT.

It also provides the same video output on one of the EGA card's RCA jacks which are usually wired to the unused feature connector and nowhere else, so by default do nothing.

Monochrome composite video feeding into the monochrome CRT, will be a bit clearer than colour composite video feeding into the monochrome CRT like the regular IBM CGA card does. EGA cards also have other advantages (but slightly reduced CGA compatibility). You still get 16 shades of grey.

This is approved for the IBM EGA card only. It will likely work on third party EGA cards too, but hasn't been tested on such.

Based on the schematic here.