Smart key
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 S-Class,[1] after the design patent was filed by Daimler-Benz on May 17, 1997.
[2] Numerous manufacturers subsequently developed similar passive systems that unlock a vehicle on approach — while the key remains pocketed by the user.
Depending on the system, the vehicle is automatically unlocked when a button or sensor on the door handle or trunk release is pressed.
Some models, such as the Ford Escape, even have settings to prevent the vehicle from exceeding a maximum speed if it has been started with a certain key.
In 2005, the UK motor insurance research expert Thatcham introduced a standard for keyless entry, requiring the device to be inoperable at a distance of more than 10 cm from the vehicle.
[citation needed] In an independent test, the Nissan Micra's system was found to be the most secure, while certain BMW and Mercedes keys failed, being theoretically capable of allowing cars to be driven away while their owners were refueling.
The device was designed with the cooperation of Siemens Automotive and Huf exclusively for Mercedes-Benz, but many luxury manufacturers have implemented similar technology based on the same idea.
[citation needed] In addition to the SmartKey, Mercedes-Benz now integrates as an option Keyless Go; this feature allows the driver to keep the SmartKey in their pocket, yet giving them the ability to open the doors, trunk as well as starting the car without ever removing it from their pocket.
The metal key is used for valet purposes such as locking the glove compartment and/or trunk before the SmartKey is turned over to a parking attendant.
The system works by having a series of LF (low frequency 125 kHz) transmitting antennas both inside and outside the vehicle.
The hardware blocks of a Keyless Entry / Go Electronic control unit ECU are based on its functionality: The smart key determines if it is inside or outside the vehicle by measuring the strength of the LF fields.
However, in every Keyless Entry / Go system provisions exist to avoid a successful two-way communication via RSA.
Depending on the electric car architecture, the following are some Control Systems that can be enabled or disabled: Another possibility is using a motion sensor within the key fob.
The power delivered to the internal LF antennas has to be tuned to provide the best performance i.e. minimum dead spots and maximum average overshoot.
Most smart key batteries are temperature sensitive causing the fob to become intermittent, fully functional, or inoperative all in the same day.
