How can you check if air is reaching all the brakes on the trailers?

Question

Accepted Answer

Open the emergency line shut-off valve at the last trailer and listen for air escaping. Then open the service line valve and listen, for air escaping.

Question:

How can you check if air is reaching all the brakes on the trailers?

Correct Answer:

Open the emergency line shut-off valve at the last trailer and listen for air escaping. Then open the service line valve and listen, for air escaping.