| 摘要 |
A keyless entry system for an automobile is described. The keyless entry system comprises a radio frequency identification (RFID) tag that has been programmed to selectively unlock an automobile when the RFID tag is within a predetermined distance and, optionally, to lock the automobile when the RFID is outside the predetermined distance. An interrogator housed on or within the automobile comprises an actuatable RF signal generator for transmitting an electromagnetic signal and a time-out circuit. Regardless whether the programmed RFID tag is detected, or not, the RF signal generator transmits a first electromagnetic signal having a first limited total continuous transmit time, followed by an interim period of a defined length where the time-out circuit renders the interrogator incapable of transmitting the electromagnetic signal, followed by the RF signal generator transmitting a second electromagnetic signal having a second limited total continuous transmit time.
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