Littelfuse Polyswitch Resettable Fuses - Raychem RUEF400, The Littelfuse Polyswitch is a resettable device that performs like a fuse under overcurrent conditions, but is unique in that it will reset.
As soon as an overcurrent condition is reached the Polyswitch heats up to its trip temperature.
Littlefuse RUEF400 4.
0A Polyswitch Fuse