The heating device is an overhead ceramic heater. There's not a very good way to put it "on" The heating device.

My probe is inside the tank but I've never had an issue with it being there and I have three separate thermometers in the tank so I'm not worried about my temperature. (I replaced the old one with two digital ones but I kept the old one because it's stuck to the back of the tank and I figured might as well leave it!). My ball also never messes with them. Thank you though!