Abstract: A transponder-responder system is provided which comprises a home station and at least one remote station. A transmitter at the home station periodically generates interrogation pulses by means of a directional sweep antenna across a search area. Each remote station includes a receiver and transmitter. Upon receipt of an interrogation pulse by the remote station receiver and while enabled, the remote station transmitter transmits a digitally encoded response signal which is received by a receiver at the home station. Upon receipt of the response signal by the home station receiver, timing circuitry at the home station determines the distance between the home and remote station by measuring the elapsed time between the transmission of the last interrogation pulse and the receipt of the response signal. Additionally, the home station includes circuitry which determines the rotational position of the sweep antenna and circuitry which decodes the response signal.

Abstract: A transponder-responder system is provided which comprises a home station and at least one remote station. A transmitter at the home station periodically generates interrogation pulses by means of a directional sweep antenna across a search area. Each remote station includes a receiver and transmitter. Upon receipt of an interrogation pulse by the remote station receiver and while enabled, the remote station transmitter transmits a digitally encoded response signal which is received by a receiver at the home station. Upon receipt of the response signal by the home station receiver, timing circuitry at the home station determines the distance between the home and remote station by measuring the elapsed time between the transmission of the last interrogation pulse and the receipt of the response signal. Additionally, the home station includes circuitry which determines the rotational position of the sweep antenna and circuitry which decodes the response signal.