How many circuits are present in a standard air brake system?

In a standard air brake system, there are typically two main braking circuits: the service brake circuit and the emergency brake circuit. The service brake circuit is used for normal stopping, while the emergency brake circuit activates in situations where the primary braking system fails, ensuring that the vehicle can still be brought to a stop.

While some advanced systems might have additional circuits for enhanced functions or specific applications, the core design of standard air brake systems primarily revolves around these two circuits. Understanding the functionality and redundancy of these circuits is critical for ensuring safety and reliability when operating large commercial vehicles. It is important to grasp this basic concept, as it forms the foundation for addressing more advanced braking systems and their components in further training or examinations.