When Envelope (ENV) is selected as the Panning source, Panning (as shown in the Panning display) is controlled by the audio signal and the Envelope section controls.
When the Side-Chain Input selector (the key icon) is enabled, the audio for the Envelope Detector is taken from the side-chain input rather than the current track. Select the Side-Chain Input using the Pro Tools Key Input selector at the top of the plug-in window.
The Threshold slider sets the amplitude level required for the Envelope Detector. The LFO Envelope Detector light blinks brighter when audio is detected above the threshold.