Epson 500 Series - Manual (Page 21)

Opening the Screen
Connecting the Trackball
Your computer package includes a, trackball, which you connect to
the MOUSE port on the left side of the computer. Although the KB
and MOUSE ports look the same, they cannot be used
interchangeably. Be sure to plug your trackball into the MOUSE
port to avoid damaging your system.
1-6 Setting Up the Computer
To open the LCD samm, place the computer on a level surface.
Facing the front of the computer, slide the release latches toward
the sides and lift up the screen.