Low-Pass Filter

The 24dB VCF module is a lowpass-filter that follows the famous cascade invented by Moog.
2x voltage control of cut-off frequency.
Voltage control of resonance ("emphasis").
2x audio inputs, the first of which has level pot and is normalled to the output via feedback loop.

http://www.mfberlin.de/Produkte/Module/VCF/VCFe/vcfe.html