What directs reservoir air into the brake cylinder during a service brake application?

The control valve is responsible for directing air from the reservoir into the brake cylinder during a service brake application. When the engineer activates the braking system, the control valve receives a signal from the automatic brake valve or through the service line that indicates a need to apply the brakes. In response, the control valve opens to allow compressed air stored in the reservoir to flow into the brake cylinder. This flow of air creates the necessary pressure to engage the brakes, effectively slowing or stopping the train as required during operation.

The control valve thus serves as a crucial component in the air brake system, ensuring that the application of the brakes is controlled and responsive to the engineer's commands. It orchestrates the distribution of air pressure needed for braking, enabling precise control over the train's deceleration or stopping.

Other options like the automatic brake valve, service line, and brake pipe serve different functions in the air brake system. While the automatic brake valve is involved in the overall braking process, the control valve specifically manages the reservoir air into the brake cylinder. The service line primarily connects various components but does not directly control air delivery. Similarly, the brake pipe is part of the system that maintains the air pressure needed for operations, but it does not directly handle the application of air to