Automatic Frequency Control (AFC) applies to tuning in radio and TV receivers to keep it on frequency. It is also sometimes refereed to as Automatic Fine Tuning (ATF). The AFC circuit in the receiver device aids in reducing the tuning error of a TV tuner that is almost on proper frequency for a desired channel. In modern sets with digital tuners this feature is usually available and can't always be switched off. There are circumstances under which AFC is better switched off but in general use it is beneficial.
