| 摘要 |
A plurality of radio base stations connected to a network are divided into radio base stations of the upper-level version having a specific function and radio base stations of lower-level version not having the specific function. Each portable telephone has a cell selecting function of receiving message information transmitted from each radio base station, detecting the cell having the highest radio quality indicating adequateness to communication from the message information, and selecting the detected cell as the cell to which the portable telephone belongs. The portable telephone is characterized by enabling the user to select either an upper-level version communication mode in which the portable telephone connects and communicates only with the radio base stations of the upper-level version or normal communication mode in which the portable telephone connects and communicates with all the radio base stations.
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