Radar is very easy to understand if we use a flashlight example. Think of a guard performing his security check at night. From hundreds of metres away we are able to see his progress as he searches back and forth in the dark - yet, the guard can't see us. In fact, the guard can turn the flashlight directly at us and still never see us! Why? Because in order for us to become visible to the guard, there must be sufficient light reflected off of our clothing and returned to his eyes before he can see us. Notice - we can always see the flashlight even though the guard can't see us. That's because we need only a small amount of light from the flashlight to see it in the dark. We have the advantage.

A good radar detector works the same way. From far away and from any direction, a good radar detector can detect the energy from a radar gun, (like the light from the guards flashlight) - but the radar gun will never see us until it is much closer and is aimed directly at us. Again, just like we are able to see a guard's flashlight from a great distance even though he can't see us, a good radar detector has the advantage - we can see the radar gun from any direction and from much farther away before the officer ever sees us.