My problem visualizing this is - how does the second relay valve, I'm assuming installed by AFO, get it's signal to operate. Is another service line installed from the foot valve to this relay valve? Does the R12 receive it's air supply from one of the main system tanks? If not, where does the air supply come from? And what is the purpose of the small air tank shown in the earlier picture? Does it supply the cylinder in the toad that operates the brake? I took a brief look at their web page but didn't see any schematics.