The BOSS TR-2 Tremolo is designed to provide guitarists with classic tremolo effects in an easy-to-use compact pedal. Dedicated Wave, Rate, and Depth knobs provide a multitude of effect possibilities.DC IN JackIt accepts the connection of an AC Adaptor. By using an AC adaptor, you can play without being concerned about how much battery power you have left.Rate KnobThis knob adjusts the rate of the tremolo. The further you move the knob clockwise, the faster the rate becomes.Wave KnobThis knob controls the waveform of the tremolo. You can go from smooth volume changes to more dramatic ones.Output Jack and Pedal SwitchThe output jack is used to connect an amplifier, and the pedal switch turns the effects on/off.ThumbscrewWhen this screw is loosened, the pedal will open, allowing you to change the battery.Check IndicatorThis indicator shows whether an effect is on/off and doubles as the battery check indicator. The indicator lights when an effect is on.Depth KnobThis knob adjusts the depth of the tremolo. When it is turned fully counterclockwise, no tremolo effect will be created.Input JackThis jack accepts signals coming from a guitar or other musical instrument or another effects unit.