| 摘要 |
The invention consists of an apparatus and an operative method with which a transponder is detected and read in a controlled passageway. The detection and reading apparatus is programmed to control its transmitter coil (Tx) so as to repeatedly emit a detecting electromagnetic field only for a brief interval of the transmission signal period, of a sufficient duration to allow the transponder to emit its presence signal. When the detection and reading apparatus receive the transponder's first presence signal, the transmission coil (Tx) is instructed to emit an electromagnetic field of longer duration, sufficient to activate the transponder so that it emits its own complete coded signal so that it can be read and decoded. In the following periods the transmitting coil (Tx) is instructed repetitively to emit an electromagnetic field that remains of brief duration as long as the transponder remains in the controlled passage. When detection of the transponder presence signal terminates, the detection and reading apparatus resets itself and returns to the control of the emission of electromagnetic fields of brief duration.
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