Let me summarize your statement, two kinds of AGC are here, which areahmad_abdulghany said:Hello
AGC (Automatic Gain Control) is used in Recievers mainly to stablize output level of the recieved signal. there are some types of AGC such as Normal AVC and delayed AVC.. Normal AVC just apply a function that have shape like Vo=(1-exp(-AVin)) i.e. this function will cause small signals to be aggressively enlarded whil large signals are less enlarged.. wherease delayed AGC enalrges all signals smaller than certain level with constant gain and work as normal AGC for signal higher than this limit.
I hope this helps
Tell me if something isn't clear.
I saw the term "Keyed AGC" from the datasheet of PHILIPs car radio.biff44 said:The Bell Labs technical term that is generally used in the US is "delayed AGC", not keyed AGC