What does the term "air reservoir" refer to?

The term "air reservoir" specifically refers to storage tanks designed to hold compressed air for the braking system. These reservoirs play a crucial role in air brake systems, as they ensure there is a sufficient supply of air available for the brakes to function effectively. When the brakes are applied, air is drawn from these reservoirs, providing the necessary pressure to actuate the brake system components.

Having adequately sized and functioning air reservoirs is vital for maintaining proper brake performance and response time, especially under varying operating conditions. This storage capability is essential, as it allows for temporary supply during peak demands when the brakes are repeatedly engaged.

The other options focus on different components or functionalities unrelated to the definition of "air reservoir." Valves manage airflow but do not store air themselves, while components that convert air into mechanical energy describe a different type of machinery. Tools for checking air pressure are important for maintenance but do not perform the function of storing air, distinguishing them clearly from the role of an air reservoir.