Please explain the difference between the Gain and Sensitivity on a UR1 bodypack
The Sensitivity adjustment has three large steps: +15 dB / 0 dB / -10dB. +15 dB might be used for a lapel mic on a soft talker. -10dB might be used for a heavy metal guitar.
The Gain adjustment is fine tuning (1 dB steps) once the general range is selected by the Sensitivity control.
A mixer might have a three position input switch of Mic / Aux / Line; that is equivalent to the UR1 Sensitivity. The mixer might also have a Trim control for fine adjustments: that is the equivalent of the UR1 Gain.