Even without radios, there are lots of different ways to get data in and out of an airgapped system. Examples include everything from sound (especially ultrason

Even without radios, there are lots of different ways to get data in and out of an airgapped system. Examples include everything from sound (especially ultrasonic beacons etc. as these are used for cellphone marketing today) to more esoteric stuff like flashing the LEDs in a specific pattern or even changing the cpu temperature to specific levels.