Practice question

What is the correct procedure when connecting (coupling) dual-line pneumatic brake hoses from a tractor to a trailer?

Connect the red (supply) line first, then the yellow (control) line
Connect the yellow (control) line first, then the red (supply) line
Connect the red line only; the yellow line is needed only where the trailer has ABS
Connect both lines at the same time so that the pressures equalise

Answer: B — Connect the yellow (control) line first, then the red (supply) line

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