This is a unique tremolo effect that also slows down the tremolo speed as the volume decreases. (Adjustable with the Peak knob. Turning it all the way down turns the effect OFF, and it functions as a normal tremolo.) There is some wear and tear from age, but there are no operational issues. ◻︎ 3 tremolo types selectable: Optical, Bias, and Stereo Pan ◻︎ Peak knob: Adjusts the sensitivity of speed changes based on the intensity of the sound (strong → fast, weak → slow) ◻︎ Shape knob: Allows for fine, stepless adjustment from a sine wave to a square wave ◻︎ Stereo in/out ◻︎ Tap tempo function ※Includes the main unit only.