What is the function of the air supply knob in the tractor protection system?

The air supply knob plays a critical role in the tractor protection system by controlling the trailer brakes. This knob is used to connect or disconnect the air supply from the tractor to the trailer. When the knob is pulled out, it allows air to flow into the trailer's braking system, which is essential for the operation of the trailer’s brakes. This allows the driver to ensure that the trailer can be safely towed and that the brakes will function correctly.

Understanding the significance of this function is crucial for safe operation. Proper connection of the air supply means that the trailer is ready to respond to braking, maintaining safety on the road by ensuring that both vehicle and trailer brakes operate in unison. It's also vital to operate this knob correctly during the coupling and uncoupling process of trailers, as it affects the overall braking performance and safety of the rig.