| 摘要 |
A system is described for discriminating between a transmitted signal and background noise comprising a transmitter adapted to transmit a signal including first and second pulses, separated by a predetermined time interval; and a receiver including a pulse detector to detect pulses received from the transmitter; a delay circuit adapted to delay transmission of the first pulse for a predetermined period of time in communication with the detector to receive a pulse therefrom; and an AND gate having an output, a first input in communication with the delay circuit and an second input in communication with the detector, the time of transmission between the pulses equaling the time delay of the delay circuit, whereby the AND gate allows transmission of a signal only when simultaneously receiving pulses from the detector and the delay circuit. The system can be used in the determination of the distance between two points, or in the location of an object within an area, based upon calculation of the time between transmission of an initial signal and receipt of a return signal.
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