N_Cook wrote:

When did they first arrive and do they always have an unusual body colour?
There is a patent reference to 1977 but when would the first appearance in
domestic equipment have been ?.
Resistors that fail open circuit if a designed-in current capacity weak
point is exceeded , fuse-fashion, not just the thermal limit of the body ,
so often no overheating discolouration to the body or surrounding board


Fusible resistors have been common in the US for a very long time.
They were used in the early solid state car radios to prevent damage
when the germanium output transistors shorted. Probably started in car
radios about 1959. They were used in place of a fuse in a lot of early
line powered consumer electronics to prevent some idiot from bypassing a
blown fuse.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.