The internal jumper reconfigures the footswitching options on the Blackbird vacuum tube preamp pedal. Without the jumper the footswitches operate as labelled, that is, the ‘BYPASS’ footswitch is a bypass footswitch and the ‘CHANNEL’ footswitch selects the clean (green LED) or drive (red/blue LED) channels. If the white link is placed on both pins connecting them, the function of the ‘BYPASS’ footswitch and ‘CLASSIC/CREAMY’ switch are swapped. This is so that the user can gain access to the ‘CLASSIC’ (blue LED) and ‘CREAMY’ (red LED) channels in a live situation and the Blackbird is always engaged. Just push the jumper onto the pins. Orientation is not important.