This is the Tone-Clamp Buffer/Compressor. This pedal is actually two circuits in one pedal. The Compressor offers a classic, warm, smooth compression. The Buffer is useful for driving your guitar signal through several effects or long cable runs without losing tone. The Volume Control applies to the Compressor side of the circuit. The Blend Control mixes the Compressed signal with the Clean Buffered signal. When turned fully to the left the signal is just buffered with no compression, as it is turned to the right, more compression is added until, when fully right, the entire signal is compressed.