1. It allows to take control of the 5 channels control knobs for AUX A and B (0/5V) and PAN (-5/5V) .
  2. Unity gain control knobs for each input.

P.S.: In order to use properly SM5-EXT you need to have enabled 16 number of voices (poly sources at the top of Voltage Modular panel)

[Stereo-Mixer-5 Extension]