Access control systems are primarily used at businesses and are electronic systems which utilize key fobs, key cards, and/or smartphones to unlock/lock doors. Key fobs or cards can be kept in a wallet or attached to a keychain and when they are put close enough to a card reader next to any door with an access control system, it will unlock the door. Card readers are normally located next to a door and they use encoded radio waves for security. Some access control systems can also be accessed from a smartphone app to lock/unlock doors, add/remove cards or users and create integration rules with a security system.