It is actually literally a light bulb. Not a new idea, the PTC characteristic of the filament is taken advantage of for cheap protection. They are available as others have written, but I imagine the actual type isn't too critical.
73
-Jim
NU0C
On Mon, 19 Apr 2021 20:17:21 -0700
"k7wxk" <Mtniebs@...> wrote:
I have read that it is not a fuse, but a variable heat sensitive resistor.
Jim Shorney