COMMUNICATION SYSTEM, COMMUNICATION TERMINAL DEVICE, AND WIRELESS KEY DEVICE

摘要

PROBLEM TO BE SOLVED: To limit functions of a communication terminal device such as a mobile telephone terminal within an area at a fixed distance from a wireless key and to disable release of the function limitation unless the mobile terminal device is present nearby a user (wireless key) once the functions are limited.

SOLUTION: The communicable distance between devices varies with the level of transmission power communicated by wireless between the communication terminal device and wireless key, which is used to control the transmission power according to the situation. In concrete, the transmission power from at least one of the devices is made smaller when the function limitation is released than when the function limitation is imposed. Further, the transmission power is increased to the original transmission power when function limitation is imposed again after the function limitation is released.

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