The DIST-13 is a distortion effect module.
The drive knob boosts the gain of the input signal up to a factor of 30.
The tone knob adjusts the high frequency content of the distortion output.
The mix knob blends the original signal with the distortion effect.
The control voltage amount knob applies the CV socket input to the drive amount.
Control voltage input for drive modulation.
Distortion effects are typically placed on the output of a synthesizer, but with a modular design, you can place the distortion effect anywhere. For example, you can distort an oscillator before it goes into a filter.