{{http://www.gamesx.com/grafx/db9.jpg}}

^Pin^Function^
|1|Button 1|
|2|Button 2|
|3|Button 3|
|4|Button 4|
|5|Horizontal pot|
|6|Vertical pot|
|7|+5v|
|8|GND|
|9|-5v|

The joystick potentiometers work by voltage division between -5V and +5V. Actually, it uses a couple of resistors on each side to make it more like -3.4V to 3.4V.

^  Vertical  ^^  Horizontal  ^^
^  Pin 6  ^^  Pin 5  ^^
|Up|+3.4v|Left|-3.4v|
|Center|0v|Center|0v|
|Down|-3.4v|Right|+3.4v|