Abstract: A portable radio telephone is provided, which turns off or on automatically the communication function when the user enters a prohibited area or exits from the area, respectively, and at the same time, the built-in additional convenient functions are kept operable even after the communication function is turned off. The telephone comprises: (a) a radio section for receiving an input radio signal and/or transmitting an output radio signal; (b) a power supply controller for controlling supply of electric power to the radio section responsive to reception of a power-off signal; the power-off signal being transmitted from a power-off signal transmitter provided in a prohibited area where use of a portable radio telephone is prohibited; and (c) a power-off signal sensor for sensing reception of the power-off signal to notify the power supply controller of reception of the power-off signal.