testing trailer emergency brakes versus testing trailer service brakes

The above photograph comes from the Georgia CDL Manual. I'm confused because the description of how to test the trailer emergency brakes looks so similar to the description of how to test the trailer service brakes. My only guess as to how there might be a difference between "how to test the trailer emergency brakes" and "how to test the trailer service brakes" is that to test the trailer service brakes, you pull a knob or valve that is different from the (red colored) TRAILER AIR SUPPLY knob. The description for how to test the trailer service brakes says to apply the brakes with the hand control (trolley valve). At first, it did not occur to me that the "hand control" could be something different than the TRAILER AIR SUPPLY knob, so I was totally baffled. I still am not 100% sure that the hand control is something distinct from the TRAILER AIR SUPPLY knob.

Here is a photograph of the only "brake knobs" on my truck:



In the instructions for how to test the trailer service brakes, is the hand control (trolley valve) something different than the (red colored) TRAILER AIR SUPPLY knob in the photograph above?

 

I've drove in at least 20 different trucks in my career, and the only time I have seen one of those trailer brake levers is in the photograph you posted on this thread.

 

I have driven International, Freightliner, Peterbilt and Kenworths, and none have had a trailer brake handle.

 

In seven years, I never saw a truck with a lever. I am on hometime right now. I might take a photograph of the interior of my truck and show you how i don't have a lever when i go back from hometime.