This device found its way into many Eddie Van Halen recordings, adding a shimmering velocity to guide passages or a more dramatic swoosh to make muted strums. Not just for guitars, but also for bass, keyboards and even vocals. Vary the speed from a subtle, long cycle to a fast, watery warble...and a myriad of vintage vibes in between. Power: Single 9 volt battery or Dunlop ECB-003 AC adapter - Controls: Footswitch turns the effect on or off (red LED lit) Speed knob varies the phase sweep speed.