Patent ID: 7126453

Claim:
In a motor vehicle, a keyless latch system comprising: an electrically openable door latch; a coded transponder adapted to be carried by a user; vehicle-mounted interrogating means adapted when enabled to remotely coact with the transponder for unlocking the latch when the transponder holds a predetermined code; a door handle associated with the latch; a first capacitor element on the handle; a control for determining the capacitance between the first capacitor element and the user when the user is near the vehicle for enabling the interrogating means only when the capacitance between the element and the user passes a predetermined threshold, said control defining for said first capacitor element a capacitive sensor field within a detection range of said element and a response range within said detection range and bounded by said threshold so that interrogation commences only with a capacitance change in said response range, said control determining said capacitance change by charge/discharge cycling of the condenser formed between the element and the user; an actuator for locking the latch; a second capacitor element on the handle separate from the first capacitor element; and control means which is only effective when the latch is not locked connected to the actuator for determining the capacitance between the second element and the user when the user is near the vehicle for locking the latch when the capacitance between the second element and the user passes a predetermined threshold.