Answer :
The trailer hand control valve supplies air to the trailer service brakes through the trailer supply circuit when the system is functioning normally.
In a typical FMVSS 121 compliant tractor-trailer, the trailer hand control valve plays a crucial role in operating the trailer service brakes. When the driver actuates the trailer hand control valve, it activates the trailer supply circuit, which is responsible for supplying air to the trailer service brakes. This circuit ensures that the trailer brakes receive the necessary pneumatic pressure to engage and provide braking force.
The trailer supply circuit is designed to connect the tractor's air brake system to the trailer's braking system. When the driver operates the trailer hand control valve, it opens the air passage, allowing compressed air to flow from the tractor's brake system to the trailer. This air supply reaches the trailer's service brake chambers, enabling them to engage and generate braking force.
The trailer supply circuit acts as a conduit for transmitting the compressed air signal from the tractor to the trailer. It ensures that the trailer service brakes respond effectively to the driver's commands, allowing for safe and efficient braking performance. This circuit is an essential component of the overall braking system, ensuring proper coordination between the tractor and the trailer during braking maneuvers.
Learn more about Trailer brake systems
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