| 摘要 |
PROBLEM TO BE SOLVED: To simplify a signal connection system between a portable radio telephone equipment and an on-vehicle adapter by providing a portable radio telephone equipment side with a power source switch part for interrupting the input of a battery power source only when an external power source is inputted to an external power source input terminal and preventing the external power source from flowing back to the input terminal of the battery power source input terminal. SOLUTION: The power source switch part 10 operates to select a power source from one of the battery power source from a battery part 14 and a battery power source from an on-vehicle external device 20 based on the presence/absence of the voltage of an external power source line 30b being an external power source supply line and to supply it to the portable radio telephone equipment. In a state where an ignition signal line 20a is turned off, operation power source to the equipment 1 is supplied from the battery part 14 and the equipment 1 is controlled by a control part 7. In a state where an ignition signal line 20a is turned on, the external power source is supplied as the operation power source from the battery of a vehicle to the equipment 1 through the device 20. |
