UR44: Side chain compression in channel strip?

Out of curiosity more than anything: My understanding of side chain compression involves compressing a signal based on the gain from a separate input. The “morphing channel strip” includes controls for side chain Q, Frequency and Gain, but I don’t see a way to specify the side chain input bus or route another signal into it. What am I missing?

Thanks in advance.

Answered my own question. It uses the input itself as the source, but the F and Q parameters allow you to emphasize or de-emphasize a frequency notch that influences the amount of compression. For example on a vocal input, boosting the side chain gain for frequencies in the 4-10kHz range, it will compress the sibilance more than the rest of the input, to “de-ess” the vocal. It’s considered a side chain, even though there is no separate source, because the EQ is applied only as the control, not to the actual output.