This Module is currently available.
Dual Ring Modulator
There are two types of ring modulator used in audio synthesis: AC-coupled, and DC-coupled. The AC coupled ring modulator is the most common. Simply described, this accepts the input of two sources with frequencies X and Y, and outputs a single signal with component frequencies: X+Y and X-Y. The original signals are suppressed, so you only hear these "sum" and "difference" frequencies.
The frequencies contained in the new signal will rarely be harmonically related, so ring modulation is well-suited to producing clangorous and metallic tones. If the inputs are harmonically rich the output will be a complex waveform, often harsh, and possibly unusable for all but sound effects.
If one of the inputs is a modulation (envelope or LFO), a ring modulator acts as a voltage controlled amplifier (VCA), and the amplitude of the output signal will be proportional to the voltage of the modulation.
Each ring modulator offers two inputs and one output. There are no controls.
The x-in is normalized to the y-in in both units (for frequency doubling). Additionally the output of the upper ring modulator is normalized to the x-in of the lower ring modulator.
https://www.analoguesystems.co.uk/index.php/as-modules/rs-610n
These merchants probably sell this module. Huh?