PORTABLE RADIO TELEPHONE AND POWER SUPPLY CONTROL METHOD THEREOF

PROBLEM TO BE SOLVED: To enable use for a while without recharging or replacing a battery by employing one of set voltages higher than an end voltage as a cut-off volt age, turning a power switch on under cut-off state and starting power supply while indicating the residual time corresponding to the cut-off voltage if the battery voltage is higher than the end voltage. SOLUTION: When disconnection of power supply is determined because nothing is displayed on the screen of LCD 7 in a portable radio telephone, a power switch 21 is connected by pushing a power supply button on a key pad 6. A CPU 2 performs initialization, e.g. initial setting, detects the voltage of a secondary battery 19 and decides whether that voltage is connectable with a power supply based on the value at a cut-off voltage section. The value at the cut-off voltage section has been rewritten to a call end voltage and if it is lower than the value at the cut-off voltage section, power supply is interrupted forcibly. If it is higher than the value at the cut-off voltage section, the call tame is extracted and displayed on the LCD 7 before entering a waiting mode.