Is this the connection? There seems to be two of them drivers and passengers side.
Yes. There are two connections, one is
Emergency that connects to the red hose on the trailer, one is
Service that connects to the blue hose on the trailer.
Emergency is
usually the one on the right rear, service left rear.
Do test them, I have seen trucks (and trailers) plumbed opposite.
The easy way to test for sure is if you turn one on and air comes out constantly (with the tanks charged) that is the emergency side. The service side will only vent air when the truck brakes are pushed.
I tow M1082s with my M813 with no problems. The M1082 hoses cross when connected, this is correct.
Cheers