How do you add air to trailer tires without air inlet ports?

Sometimes I get trailer tires that don't have air inlet ports to add air to the tire. Below is a photograph of such a tire:

These trailer tires without air inlet ports are always tandem tires, and there are always white tubes going from the hub oil seal to the inner tire on these trailer tires without air inlet ports. The only way I know of to check the air pressure on these tires is by thumping the tread with a hammer. There is no air inlet port to use a tire air pressure gauge. One time I had a trailer tire without an air inlet port like in the picture above, and the inner trailer tire was low on air. I didn't know how to add air to the trailer tire. If the outer tire was low on air, I wouldn't be able to add air to the outer tire either.

How can a person add air to a trailer tire in the photograph above?

 

By "red button", do you mean the red brake valve?

I have the light. The light does not light up with the key on and red button in.

 

If you click on my screen name, a new menu will pop up. Put the cursor over the number of messages I have made, and then click your mouse on that number. That will give you a list of all the messages that I've made. Then go back through my old posts to see if I drew pictures in other threads. If you'll read my previous posts, you will also find out how many years of experience I have. I will give you a hint though: It's less than 12 years of experience.

 

I don't care what you believe.