70s Zipper Envelope Filter in used physical condition but in perfect working order.

The vintage Electro-Harmonix Zipper is a dynamic analog auto-wah/envelope filter. 

Controls:

• Range: sets the frequency sweep range of the filter. Clockwise widens and brightens the sweep, while anti-clockwise creates a deeper, darker response.
• Q Knob: controls the resonance and sharpness of the filter peak. Cranked it produces a sharper, more accentuated and vocal gurgle.
• Attack Toggle: selects the response speed of the envelope follower.
• • 1: a slower, smoother filter movement closer to a traditional wah.
  • 2: a fast and percussive response.
• BP/LP: switches the core filter type.
• • BP (Band Pass): focuses the midrange giving a brighter, punchier, more vocal-like bite.
  • LP (Low Pass): passes lower frequencies through for a warmer, deeper tone.