In electronics, a limiter is a circuit that allows signals below a specified input power or level to pass unaffected while attenuating the peaks of stronger signals that exceed this threshold. Limiting is a type of dynamic range compression. Clipping (audio) is an extreme version of limiting.
Bass instrument amplifiers and power amplifiers are more commonly equipped with limiter circuitry to prevent overloading the power amplifier and to protect speakers. Electric guitar amps do not usually have limiters.
In FM radio
An FM radio receiver usually has at least one stage of amplification for this purpose. It provides a constant level of signal to the FM demodulator stage, reducing the effect of signal level changes in the output. If two or more signals are received at the same time, a high performance limiter stage can greatly reduce the effect of the weaker signals on the output. This is commonly referred to as the FM capture effect.
Generally, FM demodulators are not affected by amplitude variations, since the baseband is contained in the frequency deviations. Some detectors, including the ratio detector, inherently limit gain by a nature of the circuit design. In AM radio, the intelligence is located in the amplitude variations, and distortion can occur due to spurious signals that could cause the baseband to be misrepresented.