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question 12

Essay

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Definitions:

Trailer Service Brake

The trailer service brake is the main braking system of a trailer, activated by the driver to slow down or stop the trailer while in motion.

Treadle Valve

A dual-circuit service brake actuation valve that meters air from the primary and secondary service reservoirs to the service lines and brake chambers. Also known as a foot valve.

Permissable Leakage

The maximum amount of leakage allowed by regulation or specification, often referring to fluids or gas.

FMVSS 121

Federal Motor Vehicle Safety Standard 121, which specifies the requirements for air brake systems in heavy vehicles, ensuring safety and reliability.