Gain Control

"Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers,
the purpose of which is to maintain a suitable signal amplitude at its output,
despite variation of the signal amplitude at the input.
The average or peak output signal level is used to dynamically adjust the gain of the amplifiers,
enabling the circuit to work satisfactorily with a greater range of input signal levels."