| 摘要 |
An identification system in which power drain is minimized is disclosed. The system comprises a reader (10) including a first signal generator (12) for generating a first signal (F1) which is then radiated by an antenna (17). An identifier (11) is shown which includes an antenna (20) for receiving the first signal for transmission to a signal modulator (32) which operates to modulate the first signal in accordance with a preassigned code for the identifier. The modulated signal is then used to periodically unload or change the reactance of the antenna (20) which action in turn changes the reactance of the reader antenna (17) and the consequent voltage on the reader antenna. By detecting the change in the voltage on the reader antenna the code of the identifier is determined. Power is used efficiently by low frequency oscillation within the signal modulator, by unloading during modulation, and by changing circuit reactance without changing the circuit load.
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