The RPC is a variable active control that boosts the high frequency response up to 6 dB at 4000 Hz, while simultaneously reducing low frequency response. Its potentiometer controlled circuitry allows you to sweep from natural sound to accentuated highs typical of single-coil pickups. Like the SPC, it can be wired to one pickup or at the output of the guitar. In the Box : Output jack and battery clip set.