Hi Barry.
The Nitrous has the capability to compress using local or external Control Voltages or Both.
This means that several configurations can be utilized for Stereo Compression. .

1/ Local C.V
This is normal operation . When the compressor switch is engaged the detector circuit reads the audio and generates the appropriate Control Voltage signal via Attack and Release time settings.
It is possible to do stereo compression in this mode , this is compression from the sides.
Each channel is perfectly isolated from the other although it is important to closely match up the compression settings between the units.

2/External C.V
When other requirements such as ducking are required the Nitrous can slave off another Nitrous to accomplish this.
With the C.V switch engaged but the main compression switch off , the Nitrous can read external C.V without looking at its own C.V.
Gain reduction is still registered on the LED display.
In a Stereo setup using two Nitrous , this could mean that either A or B could be master .
Compression appears from the top in such a setup , however is actually driven by the nominated side that is the master....

3/Internal and External C.V.
In this configuration , both units need to have the C.V switch engaged as well as the main compression switch on.
Using the Threshold controls one can set up the appropriate mix of both channels to accomplish the desired centred compression.... although it is recommended to match up the settings between the units.

In this case compression appears from the top but is driven by both channels.The Attack and Release parameters are added together and the 'Tight' switch is added as well.

Information sent down the C.V connection on the back: Threshold , Ratio , Attack , Release , Tight switch On/Off.

You can also hook up two Nitrous to process a single (mono) signal with two different time and Ratio settings yet only use one Nitrous in the signal path.This is useful for Vocal for example where you may want to run a peak limiting Nitrous with it's own settings to re-act to transients ( high ratio , fast attack and release , tight switch on ) and a softer soak type Nitrous that re-acts to the average energy in the signal ( low ratio , slow attack and release , tight switch off ).....

...Blah , blah , blah ...... 8-)

8)