I've found in different trucks and buses, etc.... An "H" button which, when pressed, activates a braking system. This system is only available when the vehicle is immobilized.
Which brakes are activated? How does it work? Why do they stay on even if the button is deactivated and until the driver makes an action to restart motion?
Whenever I try to search for this I continuously get unrelated answers about how brakes work. I just want to know about that subsystem.