Final answer:
A hydraulic combination valve includes a pressure regulator, a metering valve, and a brake failure warning switch, each ensuring different aspects of braking performance and safety.
Step-by-step explanation:
The hydraulic combination valve typically consists of three main components which are: pressure regulator, metering valve, and brake failure warning switch. The pressure regulator modulates the hydraulic pressure to ensure consistent braking. The metering valve balances the pressure between the front and rear brakes for controlled braking. Finally, the brake failure warning switch activates a warning light in case of a hydraulic failure.