The Dreamcast VGA box is a peripheral that can be used instead of the standard video lead. In addition to the RCA Composite and audio connectors, the VGA box has a Super Video (YC) connector, and of course the VGA connector. Additionally, it sports a 2.5mm stereo connector intended for connecting a pair of PC speakers.
VGA / Video selector | v n +------------------+ SVHS --> | | <-- VGA connector Composite RCA --> | | Left audio RCA --> | | <-- Stereo line out Right audio RCA --> | | for PC speakers +------------------+ | | \ / || || To DreamcastBoth the RCA audio and the PC speaker audio connectors are active at all times. However, you'll only get video on either the VGA connector, or the SVHS and Composite connectors, at one time (selected with the switch). This is because the box is not a scan doubler, it actually makes the Dreamcast change it's scanrate beteen 15 and 31 kHz. This is also the reason VGA output doesn't work with all games; the game must be able to cope with both scanrates. (The SVHS and Composite works with all games of course.)
The custom A/V connector on the Dreamcast to which the VGA box connects has the following pinout:
______________________________________ | | |1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16| \____________________________________/(Female (sort of) connector viewed from outside of console.)