Firebird 2 User's Guide
Chapter 6 – Joystick Tension Adjustment
Firebird 2 provides round movement without corners in tension settings 1–5.
Tension setting 6 provides defined corners for software calibration and for
those players who prefer corners. If your game’s calibration program requires
square corners, set the joystick’s tension adjusters to setting 6. When you finish
calibrating the game, readjust the tension to your preference.