A vehicle security system (10) that includes a knock detection means (18, 24) such as a microphone (18) configured to detect knocking on the vehicle (12) such as knocking on a window (20) of the vehicle (12). The system (10) includes a controller (26) configured to receive a signal (22A) from the knock detection means and unlock a door (28) of the vehicle (12) if the signal (22A, 22B) corresponds to a predetermined pattern.
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