What is the primary function of the control valve in the braking system?

The primary function of the control valve in the braking system is to sense pressure changes. This valve plays a critical role in regulating the air pressure in the brake system, responding to the signals from the engineer’s input to apply or release the brakes effectively. When the engineer moves the brake handle, it alters the pressure in the brake pipe, which the control valve detects. Based on this pressure sensing, the control valve adjusts the amount of air released to the brake cylinder to either increase or decrease braking forces as needed.

The other options highlight different components or functions that are not the main role of the control valve. Storing compressed air pertains more to the air reservoirs in the system rather than the control valve itself. Providing auxiliary charge is an aspect related to maintaining system pressure but is not the central function of the control valve. Increasing train speed is contrary to the function of a braking system, as the goal is to slow down or stop the train safely. Thus, recognizing the control valve's role in sensing pressure changes is essential for understanding its function in the overall braking mechanism.