From Meng Qi, via matrixsynth:

Passive dual diode ring modulator with internal connections that can be break by inserting audio plugs.
When only input 1 and 2 are used, output 1 is the ring modulation output, output 2 is the singal of output 1 being modulated again by input 2 (de-modulation output).
When input 1, 2, 4 are used, output 1 is the ring modulation output, output 2 is the singal of output 1 being modulated by input 4.
When all 4 inputs are used, it can be 2 totally indepented ring modulators.
Very versatile!”

Apparently, the cats love it.