Kept in a smoke free home-studio. Works great!

From the manufacturer:

The four handy knobs can act as active attenuators (unipolar) or attenuverters (bipolar) depending on the setting of the two-position switches above each channel.

Each input is normalled to a precision +5V DC voltage source. With nothing plugged into the jacks, each knob controls a voltage range of 0V to +5V or -5V to +5V depending on the position of the mode switch. This is great for setting up “performance macros” in your patch to control multiple parameters with a single knob.

The channels cascade from left to right, allowing you to blend up to four channels, set up a stereo mix, or apply an offset to a signal. This means that envelopes can be made bipolar, or LFOs can be made unipolar.

Features

Active/Buffered Attenuator/Attenuverter/Mixer with external signals.

Each output normalled to mix into the adjacent channel on the right making it possible to do sub mixes in groups of 2, 3 or all four channels.

2 Modes for each channel (Unipolar and Bipolar).

5v Normalled to each input.