Access control key fobs are electronic key fobs that are used for controlling access to buildings or vehicles. They are used for activating such things as remote keyless entry systems on motor vehicles. Early electric key fobs operated using infrared and required a clear line-of-sight to function. These could be copied using a programmable remote control. More recent models use challenge–response authentication over radio frequency, so these are harder to copy and do not need line-of-sight to operate. Programming these remotes sometimes requires the automotive dealership to connect a diagnostic tool, but many of them can be self-programmed by following a sequence of steps in the vehicle and usually requires at least one working key.