This is a transient voltage suppressor (TVS) manufactured by Liown that is designed to limit voltage spikes and protect a device from electrical overstress. It is a unidirectional TVS, meaning that it will only react to voltage spikes when they move in one direction, and will remain inactive for voltage spikes moving in the opposite direction. The device has three breakdown voltage ratings of 548V, 342V, and 420V, meaning it is designed to absorb electrical spikes up to the rated voltage before allowing them to be passed through. It is rated at 600W, meaning it can handle up to 600 watts of power before the TVS fails. It is also rated at 1.1A and 1uA, which are the current ratings at its breakdown voltages. Lastly, this part is RoHS-compliant, meaning it meets all of the current standards for hazardous materials in the European Union.