Air connector for Tropical?

I was watching a video on RVgeeks about using the onboard air system to inflate the tires on a DP. I have a 2004 National Tropical DP. I've always been under the impression that I don't have the fitting installed in my air system that I would need to hook a air hose to it.

So as I'm watching the video they show an air hose connector in their motorhome that came installed by the manufacturer. And while pointing it out they also mention that if you ever have the motorhome towed that the tow truck operator would need to plug into that fitting in order to unlock your brakes. I never thought of that. Without air pressure the brakes should lock up shouldn't they? So if I don't have a fitting installed and my motorhome ever needs to be towed, how would they get the brakes to release?

I started wondering about this so I just went out and got all dirty climbing around under the front of my motorhome and I don't see any types of fittings. Is anybody familiar with the National Tropical and do you know if there is a fitting installed someplace? If so where? And am I right about the brakes locking once the air pressure bleeds off? If so it sounds like I better have a fitting installed if for nothing else in case I ever have to be towed.