Which component of the brake system ensures equal application of brakes across all train cars?

The component that ensures equal application of brakes across all train cars is the electric brake circuit. This system is critical for controlling the application and release of brakes throughout the entire train, ensuring that all cars respond uniformly when the brakes are activated. The electric brake circuit communicates signals to each car's braking system, allowing for synchronized operation, which enhances safety and efficiency.

In contrast, the slack adjuster primarily compensates for the movement and slack in the braking mechanism due to wear or thermal expansion, rather than managing the overall brake application across multiple cars. The air pressure regulator is responsible for maintaining consistent air pressure within the braking system but does not directly control the synchronization of brake application. The brake control panel provides the operator with controls and feedback about the brake system, but it does not perform the function of equalizing the brake application across the train. Thus, the electric brake circuit plays the key role in achieving uniform braking response in a train.