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

Unlink
When set to unlink (up position), the controls for channels one and two are
completely independent. Unlink is generally used in mono mode. When unlinked,
automation data is written and read by each channel separately.
Note: When unlink is switched to link, channel 1 controls are copied to channel
2. Control offsets between channels are lost in this case.
Link
When set to link (down position), modifying any channel one or channel two
control causes its adjacent stereo counterpart control to snap to the same position
(channel 1 & 2 controls are ganged together in link mode).
When link is active, automation data is written and read for channel one
only. In this case, the automation data for channel one will control both channels.
Note: When link is active, changing channel two parameters from a control
surface or when in “controls only” (non-GUI) mode will have no effect.
Mono/Stereo
The Neve 33609 can operate in true stereo or dual-mono mode. This switch
determines the active mode.
Mono
In mono mode, channels 1 and 2 are completely independent and the 33609
functions as a dual-mono device, each channel with its own compressor and
limiter.
Note: To read and write automation data for both channels independently
when in mono mode, link mode must be disabled.
Stereo
In stereo mode, the left channel is fed to the channel one compressor, and the
right channel is fed to the channel two compressor. The two compressors are
constrained so that they both compress the same amount at any instant. This
prevents transients which appear only on one channel from shifting the image
of the output. Any big transient on either channel will cause both channels to
compress. The amount of compression will be similar to the amount of compression
for a transient which appears on both channels at the same time.
UAD Powered Plug-Ins Manual - 162 - Chapter 17: Neve 33609 Compressor