The discussion of the device in series with the Cannon XLR jogged
my memories of the Polyswitch, a protective device whose resistance
jumps up when sufficiently heated (via current), but goes back down
when it has cooled off.

http://www.te.com/usa-en/products/ci...e-devices.html

We ended up not using them, but now I am curious if they show up in
damaged equipment.