The air line runs to the ARB mini-compressor that pressurizes the locker. Switches inside the truck turn on the compressor, and then lock or unlock the differential. When locked, the compressor sends air to the locker, which forces a collar to slide and engage the locker so that both axleshafts are connected. This distributes power to both wheels equally, aiding traction off-road. When you return to the asphalt or solid terrain, simply flip the switch and you have an open differential for betting street handling.