| 摘要 |
PURPOSE:To miniaturize a portable telephone system and to reduce power consumption by connecting or cutting an adapter with a portable telephone set and switching a transmission antenna in accordance with use. CONSTITUTION:A reception circuit 5 is provided for the portable telephone set 1, and a reception circuit 6 to the car adapter 2. The telephone set 1 and the adapter 2 can be cut or connected. The circuits 5 and 6 convert a frequency and detect electric field intensity. They output reception signals to a comparison circuit 7 and a switch 8. The circuit 7 compares electric field intensity and controls the switch 8 so that it selects the reception signal of a higher electric field intensity level. Then, the switch 8 changes over an antenna selection switch 11 so that transmission is executed from an antenna 10 at the time of carrying the telephone set 1 and from an antenna 23 in the adapter 2 at the time of loading the telephone set 1 on a vehicle. The system can be miniaturized and power consumption can be reduced because only one between the circuits 5 and 6 is to be driven. |
