The Carl Martin Compressor-Limiter has been specially developed to incorporate the same features and sonic clarity found in high quality professional studio compressors. To achieve this, Carl Martin incorporated a variable threshold, -variable compression ratio, -variable attack and release controls and of course, a gain level.
Threshold: Working anti clockwise, determines how much of the signal will be compressed. This is also dependent on how much signal is fed from the instrument.
Comp: Working clockwise, determines how much compression is applied to the signal allowed by the threshold setting.
Resp: Working clockwise, determines the attack/release times, going from slow to fast. In general, if you want to hear the compressor working with a crisp attack you should use slow times. If you require just a silent limiting you should use fast times.
Gain: Working clockwise, sets the overall gain.
Busy: Indicates the amount of compression being applied, even in bypass mode. The brighter it gets, the more compression is being applied.You can find more detailed information under manuals.