The Dual Loop allows you to alternate between two different effects loops. It provides two switchable loops (send / return) with a single footswitch. By using a 4PDT footswitch, the unused input will be grounded. This will avoid noises when switching between loops.   Board         1 x DUal looper diy pcb Resistors         RLa    3.3k    3.3K OHM 1/4W 1% METAL FILM RESISTOR RLb    3.3k    3.3K OHM 1/4W 1% METAL FILM RESISTOR Leds         La    Green    LED 3MM GREEN Lb    Green    LED 3MM GREEN Switch 4PDT       4PDT STOMP FOOT / PEDAL SWITCH LATCHING Connector DC    2.1mm      DC POWER JACK 2.1MM BARREL-TYPE PCB MOUNT