What safety measure is in place to help when you have an unexpected drop of pressure in the CP?
A 7.2bar stop valve between the loco and the rest of the train. The area in the Loco is called CA. This ensures that is pressure falls below 7.2 elsewhere in the CP pressure in the Loco will remain at 7.2. Thus giving you enough air to use your brakes a few times. You have to be mindful that ones you have used your air it will not be replaced.