Twenty years ago a friend of mine bought himself the full fat Colin Mcrae Scooby 555 and one stipulation for the insurers was that it had to be fitted with a Tracker. Only the actual Tracker Fitter was allowed to know it's whereabouts in the car.
The final test to ensure it was operative was to shut it in a shipping container and hit the alarm button and see how long the response takes. They located it in 10 minutes.
I have worked my whole life installing and commissioning Radio Stations as had my friend and I have yet to hear an explanation that satisfies my mind as to how this works.
