Practice question

What is the purpose of the tractor protection system's trailer supply valve (red knob)?

To supply air pressure to release the tractor parking brakes
To control the flow of supply air to charge the trailer reservoirs and open the tractor protection valve
To adjust the front steering axle brake application pressure
To release the caging bolts in the trailer spring chambers

Answer: B — To control the flow of supply air to charge the trailer reservoirs and open the tractor protection valve

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