The A-122 is a voltage controlled low pass filter which filters out the high frequency content of the sound spectrum and allows the lower frequencies to pass through. The cut-off frequency determines the point at which filtering takes effect and can be controlled manually or by voltage control using the two CV inputs.
The cut-off slope is 24dB/octave using a Curtis CEM3379 chip and is very similar to the classic Oberheim filter sound (unlike the A-120 filter which is a “Moog-like” filter). Voltage controlled resonance can be controlled not just manually but by voltages as well, right up to self oscillation. In this case the filter behaves like a sine wave oscillator.