The One Loop from theSYLE allows you to engage or bypass an entire chain of pedals with one switch. The LED lets you know when the loop is on or off. With the One Loop true-bypass switching, you can even put buffered-switch pedals in the loop to make them true-bypass! Operates with a 9-volt battery or a standard 9-volt adapter with a negative center 'barrel' tip. We recommend the Visual Sound 1 SPOT.