Abstract: An electronic detection and identification system for use in the rapid identification of vehicles at a toll stop, and like uses, is provided which employs an electronic identification card that is carried by the vehicle to be identified and a fixed transmitter-receiver unit that transmits a signal to the card and receives a reflected signal therefrom. The card contains passive resonant circuitry for producing an output signal having a frequency which is a selected harmonic of the signal transmitted thereto. In operation, the card is radiated with a signal which has a freqency in the Gigahertz range and which is produced by frequency sweeping and multiplying a frequency stable RF signal. The signal reflected by the card is narrow band-filtered and RF amplitude (envelope) detected. The detection envelope, which is the "signature" of the received signals, is compared with a reference profile to determine whether a match exists.