| 摘要 |
PROBLEM TO BE SOLVED: To enable positively determining power failure of an external power source to turn on illumination, irrespective of whether or not a radio terminal device is connected to a charger, in the radio terminal device capable of radio communication with a master set, and to realize the above at a low cost. SOLUTION: A control unit 61 of a slave set 50 determines the presence or absence of voltage supply from a charger 80 for supplying charging voltage while directly receiving power supply from a commercial power source 90, on the basis of a charging voltage detected by a voltage monitoring unit 77. When determining that the voltage is not supplied, the control unit 61 transmits a request of connection with a telephone line network 100 to a master set 10 operating while directly receiving power supply from the commercial power source 90. When a response cannot be received from the master set 10, the control unit 61 judges that the communication with the master set 10 is impossible, and determines that the commercial power source 90 is in failure. COPYRIGHT: (C)2006,JPO&NCIPI |
