Moin! I have a MB 814 LK Bj. 92 without connections for a trailer brake. I would like to install a compressed air coupling for the connection of e.g. a compressed air screwdriver or an exhaust gun. As far as I know, I have to go there to the 4th circle. But where? From the four-circuit protection valve a line goes for each circle to one of the two air boilers. So each two circles share a boiler, right? Can I now simply reach the line between the four-circuit protection valve and the K There are always two circles hanging over the boiler, if I understand that correctly. But I really don’t understand all this. I hope for clever explanations! Thank you!!