1812L POLY-FUSE® PTC Resettable Fuses Littelfuse 1812L POLY-FUSE® PTC Resettable Fuses provide overcurrent protection for applications where resettable protection is desired. The compact fuses offer fast response time to fault currents and feature low resistance. Littelfuse 1812L POLY-FUSE PTC Resettable Fuses applications include plug-and-play protection for motherboards and peripherals, USB peripherals, PCI cards, and game console port protection.