Answer :
Final answer:
The trailer air supply control, or Tractor Protection Valve (TPV) control, should automatically close when the air pressure falls to between 20 psi and 45 psi.
Explanation:
The trailer air supply control, also known as the Tractor Protection Valve (TPV) control, is an important component of a truck's air brake system. It is designed to automatically close when the air pressure falls to between 20 psi and 45 psi.
