A proximity key (also called a “smart key” or “intelligent key”) is an electronic fob used for keyless entry and ignition systems in vehicles. Proximity keys pair with push-button starters, enabling drivers to unlock, enter, and start their cars without removing the fob from their pockets or purses.

The “key” transmits low-frequency (LF) radio waves to communicate with a vehicle to lock and unlock doors and start the engine when within a short range. Antennae within the vehicle identify the rolling code radio pulse generator inside the fob.