Passive Entry
A smart key is a vehicular passive entry system developed by Siemens in 1995 and introduced by Mercedes-Benz under the name "Keyless-Go" in 1998 on the W220 Mercedes-Benz S-Class (W220), S-Class, after the design patent was filed by Daimler-Benz on May 17, 1997. Numerous manufacturers subsequently developed similar passive systems that unlock a vehicle on approach — while the key remains pocketed by the user. Operation The smart key allows the driver to keep the key fob pocketed when unlocking, locking and starting the vehicle. The key is identified via one of several Antenna (radio), antennas in the car's bodywork and an ISM band radio pulse generator in the key housing. Depending on the system, the vehicle is automatically unlocked when a button or sensor on the door handle or trunk release is pressed. Vehicles with a smart-key system have a mechanical backup, usually in the form of a spare key blade supplied with the vehicle. Some manufacturers hide the backup lock behi ...
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