| 摘要 |
PURPOSE: A method and an apparatus are provided to prevent wiretap of the wiretap device disposed in the direction deviating from the direction of the base station by permitting the portable phone to transmit directional wave to the base station. CONSTITUTION: An apparatus comprises an antenna unit(1) constituted by two or more directional antennas(1-1,1-2,1-3); and an electronic unit(2) for driving the directional antennas. The electron unit has a receiving function for permitting the directional antennas to receive wave when a call is received in a portable phone; a comparing function for comparing the directional antennas to compare the sensitivity of the received wave; a transmitting function for permitting the directional antennas to transmit wave when the portable phone tries a call; and an antenna converting function for comparing receiving sensitivities of directional antennas and changing the antenna into the directional antenna having the superior receiving sensitivity during communication.
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