What is at and af in circuit breaker?

In a circuit breaker, "at" and "af" refer to different types of ratings for the device. "At" indicates the rated current of the circuit breaker, which is the maximum current the breaker can handle continuously without tripping. "Af" stands for the residual current rating, specifically in RCDs (Residual Current Devices), representing the threshold at which the breaker will trip to prevent electric shock or fire due to leakage currents. These ratings are essential for ensuring the safety and proper functioning of electrical systems.