The Q158 VCA++ module combines two VCAs along with innovative connectivity to provide a panner, fader, 3-channel mixer and ring modulator functions - all in a single-wide module.
You can never have enough VCAs in a modular system and the Q158 addresses this by providing two full-featured VCAs complete with invertable attenuators and bipolar gain controls.
The signal input and CV input for VCA #1 are normalized to VCA #2, in other words, they are automatically connected to VCA #2 unless plugs are inserted into VCA #2 jacks. This makes patching easy to create a 2-channel panner (one input panning between two outputs) and a fader (two inputs fading to one output).
Automatic connection between the two VCA channels also provides an easy way to do ring modulation (4-quadrant multiplier). Multiplying 2 audio signals produces frequencies that are the sum and differences of the originals resulting in inharmonic bell-like tones, a classic synthesizer function.
VCA channels #1 and #2 are mixed together along with a third un-attenuated channel in the center section. This gives you a 3-channel mixer with 2 of the channels having attenuators. The INVERT switch inverts the polarity of VCA #2's contribution to the mixer and is used to produce ring modulation.
Both VCAs have manual gain controls and VCA #2's invert switch provides simple signal processing functions.