The RL250-400 with PTC Resettable Fuses Through Hole RoHS is a type of circuit protection devices made by Ruilongyuan. It is designed to provide over-current protection from electrical shorts or overloads in low-voltage, low-current applications, up to 400V. It features a polymeric PTC (positive temperature coefficient) element which generates heat when an over-current is detected within the circuit. The heats causes an expansion in the PTC body, leading to an open circuit, disconnecting power to the circuit until the current returns to an acceptable level. The rated current of this device is 250mA, and it is RoHS compliant. It is also designed for through-hole mounting, making it suitable for a wide variety of PCB designs.