Pressing -3db sets up a -3db limiter. Reset disables the limiter/expander/compressor.

To create your own curve, press the Setup button. 

Attack defines the attack time of the envelope. Hold determines the duration of the envelope level before it Decays. Look at the I/O Level window to explore the results of different fader settings.

The limiter consumes processing power from your CPU. If you don't have enough power, press Reset.

The settings are also saved in the crusher-sheets. If you want to preserve the limiter settings, load a new crusher-sheet (use File | Open or the Loadlist) and select the disable option in the options window.