摘要 |
The distance to a communicating party is detected using whether or not an electromagnetic-coupled RF field formation is achieved or not as simple measurement means. If the distance to the communicating party is short, i.e., if it is possible to form an RF field, then transmission power is reduced. As a result, power consumption is reduced. Since a reduction in transmission power is accompanied by restriction of the zone in which communication is possible, leakage of information is prevented and security is enhanced.
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