A key fob is a small device that provides access to physical objects. In general, the term also refers to any decorative item a person carries with their keys, like small trinkets or souvenirs, bottle openers and even USB drives. In the automotive industry, a key fob is nowadays mainly a small device with buttons that unlock/lock the vehicle’s doors.
A key fob is the main device used in keyless entry systems. It contains a short-range radio transmitter, which sends a distinct coded signal to a receiver unit in the car when a button on the fob is pushed. That in result unlocks or locks the doors.
In addition to unlocking and locking the door, some key fobs can be used to open the drunk or to start the engine remotely so that the user can sit into a warm car on a cold morning. While a traditional key fob is an addition to the car key itself, the newer version of it works also as a key. This kind of fob is called a keyless fob.