| 摘要 |
PROBLEM TO BE SOLVED: To provide a handset capable of copying with plural modes or bands in spite of miniaturization, weight reduction and low cost by exchanging radio waves with a close base station while using the downloaded software for hardware change of a communication protocol and handset from a base station. SOLUTION: When the handset judges the necessity of a mode or band change, it is judged whether information switchable to the other mode or band is received from a base station 30 or not. When there is no switchable information, the control cycle of this time is finished. In the case of a handset with which roaming contract is not performed, it is similar to the network dedicated handset of the base station 30 that a call is cut off outside the network of the base station 30. In the case of switchable information, the handset receives a request for mode or band switching and a new communication protocol is downloaded to the handset.
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