I've been around working thinking of different projects to do for fun and came upon a thought (while driving home from working "tuning in" with my radar detector). Anyone have an idea on a design for a radio transmitter that transmits a signal to a receiver in our trucks (to tell them, say, to go ahead and come in and such) that makes a buzzer go off? (much like the way a radar detector "listens" for the Doplar Radar frequency to be hit). Range would be as far as I could get (in reality a few miles would be cool but just a few hundred yards would work too, I'm not sure on the laws for home brewed designs). Any help or suggestions would be appreciated, thanks.