At first sight the module is a quad VCA like any other: per VCA there's one input, one output as well as a potentiometer plus a CV input for controlling gain.
What makes the Black Quad VCA so special is the normalization of its outputs, from left to right. As long as the outputs 1 to 3 aren't patched, output 4 turns into a mix output. If used as a manual mixer module, the gain controls are effective from 12h position.
Another special feature is the possibility to configure or to assign CV inputs 2, 3 and 4 with jumpers. They can either be independent or normalized to the CV input to its left hand neighbor which is handy for "stereo" or dual-mono applications.
The potemtiometers have a dual function: left of 12h position they work as attenuators for the CVs. right of center an offset voltage is added to the signal, which of course rather makes sense when processing control voltages as generally audio signals should't have an DC offset.
The CV inputs expect a 10V CV in order to open completety. With envelopes the Maths does a good job; other envelopes might not provide enough amplitude.
4 signal inputs, 4 signal outputs, 4 CV inputs
3U Eurorack module, 10HP wide, 25mm deep
current draw: 38mA at +12V and 32mA at -12V