The A-122 is a voltage controlled high pass filter which filters out the lower parts of the sound spectrum and allows the upper 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 CEM3320 chip and is very similar to the classic Oberheim filter sound.
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.