The MF-103 Phaser works with two so-called comb resonance filters. Depending on the amount of the internal phase shifter circuits it is called 6-stage or 12-stage.
The 6-stage mode has 3 notches in the frequency spectrum while the 12-stage version has six of them. Both modes have distinct differences in sound. Additionally the MF-103 has a controllable feedback loop that increases the resonance or "depth" of the phaser sound. If this comb- or notch filter is being shifted thru the audio spectrum the typical "sweep sound" of the phaser is created.
In- and outputs for CVs and pedals allow external control of the parameters.