The Electro Harmonix Cntl Knob allows precise control of effect parameters via standard TRS connectors for expression pedals. This straightforward pedal turns out to be a useful tool for precisely tuning two foot-controlled settings via the EXP 1 and EXP 2 knobs, and thanks to switchable TRS polarity , it can be used with virtually any device that provides an expression connection, so you'll never have to worry about cocked wah sounds, timed modulation effects, and perfectly set volume settings. The footswitch toggles between the two set values, making it easy to switch spontaneously between two set parameter values. TRS cable included !