Drive, Tone, Level and Clean controls.Three Compressor Modes - High, Mid, OffClean Loop and Drive Loop (connect a Y-cable for send and return).Type: Analog Effect, Mechanical Switching9V DC (Battery or Power Supply)Advanced Options: By removing the bottom plate you get access to fine tuning trimmers to adjust Threshold level of compressor (THR.) and the level of Compression when mode switch is set to MID (COMP).