this is the Passive Feedback Loop Control Tool. it allows you to create a feedback loop with effects/signal processors and run a signal through them at the same time without the use of a mixer. it requires no electricity.
turns delays into howling waves of terror, distortions into nasty farting oscillators--string up a bunch of pedals and kiss your afternoon goodbye. amazing with modular synthesizers.
the knobs are for input volume, and feedback amount. the switches are to switch on and off the input, and the feedback loop.
i know the schematic is confusing, it's just hard to draw it right, i try. maybe this will clear it up a little:
the grounds coming off the jacks (represented as circles) are connected to the "ground" lugs on the jacks. the other lines going to the jacks are connected to the "tip" lugs (if 2 wires go to the jack, solder both wires on the lug). connect all the ground wires together at the other ends. hope that helps...
not responsible for injury or damage to equipment, but don't worry, never had any problems and none have been reported.