Passive Keyless Entry Switch | Cypress Semiconductor
In passive keyless entry systems, capacitive sensing is used for the detection of approach of driver to the car door handle using touch buttons or proximity. This sets up the trigger for encrypted communication between the keyfob located in the driver's pocket and the immobilizer in the car. Once authenticated, the driver is granted access to enter the car and drive away, without needing to take his key out of his pocket.
CapSense based systems provide waterproofing, environmental compensation and extended temperature performance (-40C to 125C) for use on the body of the car. These devices also provide lowest in class power consumption to enhance battery based performance.