| 摘要 |
PROBLEM TO BE SOLVED: To inhibit variations in the distance over which a vehicle door is locked or unlocked, so as to reduce the rate at which occupants feel disagreeable, by making as small as possible the influence of a change, if any, in the environment in which the vehicle stops or in the source voltage of a portable machine, in a case where the vehicle door is unlocked if the field strength of an unlock signal transmitted from a transmitter and received by an on-vehicle machine 15 is equal to or greater than a first threshold L1, whereas if the field strength is less than a second threshold L2 lower than the first threshold L1, the door is locked. SOLUTION: A plurality of field strengths D, D and so forth of the unlock signal when occupants get off a vehicle are detected while an ignition switch 18 is turned off at the time when the occupants get off the vehicle, and the thresholds L1 and L2 are varied in accordance with an average value Dt thereof. |
