Universal Audio UAD Plug-Ins ver.7.5 - Manual (Page 66)

UAD Powered Plug-Ins Manual - 66 - Chapter 4: API Vision Console Channel Strip
550L SC (Dynamics Side Chain)
This control enables the side chain function for the 550L EQ. When
the 550L side chain is active, signal output from the 550L module is
removed from the audio path, and is instead routed to control the 235L and
225L dynamics modules. The default value is Off.
Note: Both the 550L and 215L modules can both be routed simultaneously
to the dynamics side chain. In this case, the 215L precedes the 550L in the
side chain path, as shown below.
Figure 11. The 550L always precedes the side chain tap when PREDYN is active
Figure 12. Signal flow with 550L SC enabled
Figure 13. Signal flow with SC enabled in both 215L and 550L modules