Practice question

In a dual-line pneumatic brake system (Zweileitungs-Druckluftbremsanlage), what is the function of the red coupling line (Vorratsleitung)?

It transmits the braking signal only when the handbrake is pulled
It supplies hydraulic oil to tip the trailer body
It continuously supplies compressed air from the tractor compressor/reservoir to charge the trailer air tanks
It is an electrical cable that powers the rear fog lamp

Answer: C — It continuously supplies compressed air from the tractor compressor/reservoir to charge the trailer air tanks

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