The RF1940-000 is a single-pole, resettable fuse designed and manufactured by Littelfuse. It is rated for 1 Amp at 125V and is a very fast-acting fuse. The PPTC (Positive Temperature Coefficient) element inside the fuse will react to surges and overcurrents, causing a rapid rise in resistance, effectively cutting off the flow of electricity until the fault is removed. After the fault is removed and the temperature has cooled, the PPTC element will self-reset, restoring the flow of the electricity. This resettable fuse is ideal for use in residential, office, and hospital lighting circuits, small appliances, and power tools.