The manual for the Uno Synth Pro says little about the ring modulator. Just that makes sum and difference frequencies of the two inputs. And later it mentions, in passing, that, (oh, yeah), the inputs are oscillator 1 and 2.
We're left to find out that it replaces oscillator two in the mix.
We're also left to find out that it only "ring mod"s the rectangular waves.
I was wanting to ring-mod two triangle waves, but changing the waveshape around the triangle shape had no affect. Not until the waveshape is turned up into the square/pulse-width range do we get a change in ring-mod sound.
I guess it's like the ARP Odyssey ring-mod - an XOR of the two rectangular waves.
I read the manuals before purchasing gear, and was led to believe that the ring-mod would actually work on the triangle and sawtooth waves. It's disappointing to find out that it doesn't.
The manual should clearly specify what the ring-mod actually does.