The Worm Analog Wah/Phaser/Vibrato/Tremolo Pedal from Electro-Harmonix is a multi-functional modulation pedal. The unit's Mode rotary switch allows you select between the Wah, Phaser, Tremolo, and Vibrato effects. The Worm features a Range knob designed to adjust the amount of effect that will be applied to your signal, and a Rate knob that adjusts the sped of modulation for the effect. This pedal also has an Auto/Manual/Exp toggle switch, and a footswitch that engages/disengages the effect. If the effect is engaged, the Status LED will blink at the same rate that the effect modulates.