| 摘要 |
A mobile unit includes a LF antenna having a predetermined receiving frequency band and gain to receive a LF signal, a determination circuit for determining whether the LF signal received by the LF antenna is an authorized LF signal, a controller activated in response to a determination by the determination circuit that the LF signal received by the LF antenna is the authorized LF signal, a damping resistor connected to the LF antenna, a switch for enabling and disabling the damping resistor, and an antenna gain adjuster for reducing the gain of the LF antenna in response to a determination by the determination circuit that the LF signal received by the LF antenna is different from the authorized LF signal by controlling the switch in such a manner that the damping resistor is enabled.
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