The supply line is also called
- the secondary line.
- the control line.
- the emergency line. ✓
- the primary line.
Answer: C. the emergency line.
The supply line is also called the emergency line.
Why this is the answer
The daily trip inspection passage gives the industry standard air-line colours and labels the red line as supply or emergency. The air brake material also ties the trailer supply line to emergency braking: spring brakes must apply automatically when pressure in that line drops. That connection makes emergency line a fitting name for the supply line. The handbook does not use secondary, control or primary as another name for this line.
Why the other answers are wrong
- A. the secondary line. — Secondary is the name used for one of the two delivery circuits from the supply tank, not another name for the trailer supply line.
- B. the control line. — The passages mention a control valve for DD3 parking and emergency brakes, but they never call the supply line the control line.
- D. the primary line. — Primary is the name of the other dual-service circuit, not a name for the trailer supply line.
Remember it
Remember the gladhand colours: red is supply or emergency, blue is service.