The CGA/MDA to Analog RGB adapter is a passive device that converts CGA, MDA, EGA and other TTL video signals to a basic analog format for use with video scalers and capture devices. This does not affect the resolution of frequency of the signal, it just combines the intensity with each of the red, green, and blue signals for you to feed into your favourite video scaler (Extron, Retotink, etc).
It is designed primarily to plug direct into the back of a CGA or MDA card and convert it to a VGA pinout (i.e., 9-pin to 15-pin D connector) for ease of use.