| 摘要 |
PURPOSE:To switch voltage to be impressed to a local oscillation voltage controlled oscillator in a receiving part in accordance with the use of a built-in battery or an external power supply. CONSTITUTION:In the case of using a battery built in a battery part 7, power is supplied to the whole portable telephone set based upon the voltage V0 of the built-in battery. In the case of using an external power supply, voltage V1 almost equal to the voltage V0 is impressed to a terminal 8 and voltage V2 (V2>V1) is impressed to a terminal 9. A power supply switching part 23 outputs higher voltage out of output voltage from a regulated power supply 22 and the voltage V2 and supplies the voltage to a voltage controlled oscillator 14. At the time of using the external power supply, the purity of a signal from the oscillator 14 can be improved as compared with the use of the built-in battery and the influence of a disturbing wave from an adjacent channel can be suppressed. When the built-in battery is used, waiting time can be extended by suppressing current consumption. |
