The radio communicator 12 communicates with the base station 4 by radio communication through the antenna 11. The radio communicator 12 has an analog signal processor and a digital signal processor.

The analog signal processor performs amplification, an analog-to-digital conversion process, and any other process of radio signals received from the antenna 11, performs analog amplification, including a digital-to-analog conversion process, of the digital signals transferred from the digital signal processor, and transmits the analog signals through the antenna 11.

The digital signal processor encodes data transferred from the controller 13, and converts the data into digital signals such that the data can be transmitted through the communication channel of radio signals, whereas the digital signal processor decodes the digital signals transferred from the analog signal processor, and transfers the decoded data to the controller 13.

The controller 13 is mainly configured of a microcomputer formed of a central processing unit (CPU) that executes various programs, a read only memory (ROM), a random access memory (RAM), a backup RAM, an input/output (I/O), and any other component (none of them are illustrated in the drawings), and executes various control programs stored on the ROM to execute various processes. The controller 13 executes processes necessary to control the radio communicator 12.

The storage 14 is configured of an electronically erasable and programmable read only memory (EEPROM) that can electrically rewrite the content, for example, and the storage 14 stores programs and information necessary to control the radio communicator 12.