How Does The Key Fob Operate

How does the key fob operate?

The electronic key fob (Free On Board), contains several different type of signals.

The active buttons on the fob contain a radio frequency signal that sends a 40-bit code along with a function code that tells the vehicle what you want to do; lock to doors, unlock the doors, open the trunk, etc. The receiver inside the vehicle will authenticate the RF code and perform the action. This signal differs from the passive RF information that is transmitted to the antenna on both the exterior of the vehicle and inside the vehicle. The range is generally within about 60 feet but can extend further depending on the line of sight and signal strength.

On key-less proximity electronic systems the electronic key fob transmits both a low-frequency signal and a high-frequency signal to the vehicle’s antenna, which are authenticated by the vehicle’s computer module. Once the signals are authenticated, the vehicle doors can be locked/unlocked and the vehicle engine can be started. The electronic key fob has to be within approximately 6 feet of the vehicle to allow the doors to be locked/unlocked. A security feature on certain vehicles will prevent the passenger doors from being unlocked and opened until the driver decides to unlock them. Typically, if the electronic key fob is placed outside of the vehicle, the vehicle engine will not start, however, there have been some exceptions. On certain vehicles the key fob can be placed on top of the windshield or on top of the roof and the vehicle engine can be started.