Sega DreamCast System 2
A unique feature to video game consoles is Sega's Visual Memory Unit (VMU). The VMU is a memory card with its own built-in LCD (Liquid-Crystal Display) screen. When the VMU is inserted into a Dreamcast controller, the LCD screen allows players to preview their own special moves against competitors (like diagramming a play in a football game).
When the VMU is removed from a Dreamcast controller, it becomes a portable game card about the size of a credit card. By using the VMU players can save newly created characters or moves and can swap game information by connecting two VMU cards together. Up to two VMU cards can be plugged into a Dreamcast controller at one time.
The VMU also serves as its own 8-bit hand-held game platform and is very similar in design to the Nintendo Game Boy. It contains its own directional joypad and control buttons. Graphics are viewed on the VMU's LCD screen. A VMU card retails anywhere from $19.99 to $24.99, but requires its own separate battery power.
Sega's Dreamcast controller contains two slots for inserting peripherals (like the VMU card). It includes a digital joypad as well as an analog stick. The controller features a transparent view-port to see the VMU screen. There are four controller ports on the Dreamcast system.