Bypass based on a DPDT footswitch for guitar effects. LED lites when effect is activated.
BI means BOARD IN = effect board input
BO means BOARD OUT = effect board output
JACK IN (JI) and OUT (JO) are the input and output of the effect pedal.
Original schematic : http://foro.cuartitodiyer.com/viewtopic.php?f=5&t=5915
DPDT is manufactured by ALPHA (https://mybigsound.com/en/switches/55-footswit...