UAD Powered Plug-Ins Manual v5.2 - Just Music

Ratio This control determines the compressor ratio. The available values are 1.5:1,
2:1, 3:1, 4:1, and 6:1, selectable in discrete increments.
Compressor In
This toggle switch enables the compressor portion of the plug-in. The compressor
has no effect unless this switch is in the “In” (down) position.
Other Controls
The interface elements that are not directly contained within the compressor or
limiter are detailed below.
Output Gain
Gain Reduction
Meters
This control is a software-only addition not found on the original hardware. It
is an overall makeup gain stage at the output of the plug-in to compensate for
reduced levels as a result of compression and/or limiting. The available
range is –2 to +20 in 1dB increments.
The Gain Reduction Meters indicate the amount of gain reduction that is occurring
in dB. There is one meter for each channel. The gain reduction displayed
is the total reduction of the limiter plus the compressor.
Note: The meter indicator moves farther to the right as more gain reduction is
occurring. This meter behavior is opposite that of many compressors.
Link
This switch is a software-only addition that allows the two sets of controls for
each channel to be linked for ease of operation when both channels require
the same values, or unlinked when dual-mono operation is desired. The Link
parameter is stored within presets and can be accessed via automation.
UAD Powered Plug-Ins Manual - 161 - Chapter 17: Neve 33609 Compressor