NewTek TriCaster 8000 - Manual (Page 280)

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Being able to do this independently for each output too is icing on the cake,
especially for Internet streaming, as it ensures correct levels at any time.
T HRESHOLD
Sound above the set Threshold level will be compressed; the amount of compression
and the manner in which it is applied are both dictated by the other settings.
R
ATIO
A Ratio of 4:1 means that if input level is 4 dB over the threshold, the output signal
level after compression will be just 1 dB over the threshold. The gain (level) is
reduced by 3dB.
Very high ratio settings are the reason for the word “limiter” is part of the title for
this feature. The highest ratio setting will effectively reduce any signal that would
rise above the threshold all the way down to the threshold level (with the exception
of a brief period during a sudden increase in source loudness, as dictated by the
Attack setting).
A
TTACK
Attack (like Release) is labeled in milliseconds. The setting represents the amount of
time it takes for the gain to change by a specified amount.
It would not be grossly incorrect to think of this setting as changing the slope of a
graph depicting how aggressively the compressor pursues the target value (defined
by applying the Ratio setting to the amount the signal surpasses the Threshold).
Shorter values are more aggressive, while longer values are more subtle (and tend
to be less noticeable to the audience).
R ELEASE
Release is similar to Attack in many ways, but refers instead to the speed with which
the compression effect is removed as a source signal falls back on its own so that it
no longer exceeds the Threshold.