Years ago, my wife and I bought one of those mattress pads that is like an electric blanket. Because we don’t always operate at the same temperature, we bought a dual-zone pad. I love these things, they are truly nice on a cold night.
When we first put it on the bed, we accidentally reversed the controls. That first night, I would get cold, so I’d turn the temperature up, thereby frying my bride; while she was getting hot, turning the temperature down, thereby freezing me. She got hotter, and I got colder! I’m embarrassed to admit that it took us a couple of hours to figure out what was going on. This is called Positive Feedback.
When we put it on the bed for this winter, one of the controls was dead. So we went and bought another one.
We did exactly the same thing this time we did last time. Bless her heart. At least we figured it out sooner this time. Maybe they need to color-code the blanket to the controls or something.