Rabbit Ears uses both positive and negative feedback to search for and find bright lights. It comprises two identical sets of motorized ears each of which is made of a long arm driven by a small DC motor that has a current sensor and a shorter arm driven by a hobby servo motor with a focused light (actually infra-red) sensor on the end. Feedback from the current sensor is used to reverse the motion of the longer arm when it either stalls at the end of its travel (high current) or drops below a certain level -- when the arm is being lowered it uses quite a bit less power. The lower limit is adjusted upwards as the ears run so the longer arms tend to settle on a vertical position. Feedback from the light sensor makes the shorter arm lock onto the brightest source it can find.

The long arms use negative feedback to arrive at a balanced position -- using the motor current signal to reverse direction when it is out of the desired band. The short arms use positive feedback to track light -- trying to maximize the signal. The changing balance as the shorter arm moves affects the power used by the longer arm and the longer arm's position affects what the shorter arm can see, so there is also a systems level feedback mechanism.

A natural analog of this behavior can be found in plants where leaves use positive feedback to track the sun and stomata use negative feedback to balance CO2 inspiration against H2O loss.