4 inputs, 4 unipolar or bipolar outputs, a la the Doepfer A-138. The four rows of knobs correspond to the levels of inputs 1, 2, 3, and 4. The four columns across correspond to the four outputs, A, B, C, and D. When the button for each output is turned on, it switches the output to be bipolar, where right of center is positive and left of center is negative. When the button is turned off, the output functions in unipolar mode, like a regular mixer.