In the words of Old Blood Noise Endeavors:

BL-52 is a phase repeater pedal within our BL line. Phase repetition is a unique effect to OBNE – it lives between phaser and reverb, sounding almost like a room constantly changing in size and materials, with a clear repeat one moment and a diffuse repeat the next. The Clock slider allows this sound to move quickly and with fidelity, or slowly and darkly, undulating underneath the player.