[SiempreViernes]

I have a oven thermometer that has two active parts which are linked via some sort of wireless system.

One part is the one you plug the actual thermal probes into, and that then transmits data to a separate display. You can turn that one off.

Then there is the separate display that lights up and beeps and what have you: this one doesn't turn off, presumably so you can admire it say "--" whenever you're not actively measuring the temperature of something...