To attain execution of prescribed processing other than radio communication even when a voltage supplied from a battery drops and the radio communication is not available.

A CPU 1 stores a voltage level at which a communication function of a mobile telephone system 50 is stopped and a voltage level at which all the functions are substantially stopped to a storage device 4, and compares the voltage levels with a voltage fed from a battery 9a via an A/D converter 9b. The CPU 1 stops an operation of a radio communication processing equipment 3 and accepts prescribed key input from a user when the supplied voltage level is lower than the voltage level at which the communication function is stopped and higher than the voltage level at which all the functions are substantially stopped to execute the processing according to the key input thereby executing prescribed processing even when the power supply voltage of the mobile telephone system 50 drops and results in disabling for the radio communication.