On Fri, 18 Jun 2010 12:56:09 +0100, "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 ?.

Way before 1977 !

Take a look at radio and TV sets from the late 50s and 60s.
Big white or beige wirewound resistors in a ceramic housing, one
of the leads spring loaded along the edge, low temp solder blob
on the spring to keep the circuit closed.

Designed to cut open when the resistor's body reaches some 200
degrees Celsius / 400 degrees Fahrenheit.

(I think I can digg up a picture, if you want :-)

--
Kind regards,
Gerard Bok