The LMTR Limiter Effect is a high-ratio compressor that reduces output to prevent signal clipping while minimizing distortion in the process.
The threshold sets the decibel level at which the limiter affects the signal. The lower the value the more sensitive the effect. Once the signal crosses the threshold the limiter forces it to the threshold by whatever ratio required — it works like an very determined compressor.
The attack determines how fast the limiter affects the signal after it crosses the threshold. Longer attack times help preserve ambience.
Once the limiter affects the signal, it stays on for the duration set by the release.
Use the gain to compensate for signal reduction from the limiter effect. Switch the effect to bypass to ensure the signal is staying at an appropriate level. A common technique with a limiter is to limit the mix by a given decibel amount and re-compensate with the gain control, creating the illusion of a fuller mix.