| 摘要 |
The remaining level of a battery 9 is detected, and when the remaining level is lower than a specified value, supply of power is stopped to other circuits except necessary circuits 5, 7, 10 that need electric power for reading out a telephone number from a telephone number memory 13 and displaying the read out telephone number. Only the telephone directory function is remaining, and if the battery is spend and the portable telephone can not be used, at least a worst case of impossibility of any operation can be avoided. The specified value is a voltage level at which it is usually difficult to transmit and receive. The necessary circuits include the telephone number memory 13 and the display unit 7 for displaying the telephone number. It is further preferred to display it is impossible to transmit and receive, and possible to display the telephone number. |
