Automatic Level Control (ALC) is another name for:

Automatic Level Control (ALC) is a feedback system used in transmitters to prevent the output power from exceeding the linear operating range of the final amplifier. It achieves this by taking a sample of the RF output and using it to adjust the gain of an earlier RF amplification stage. Because ALC dynamically lowers the gain when the RF signal peaks too high, it effectively compresses the dynamic range of the RF signal. This keeps the average output power high without overdriving the amplifier. Therefore, ALC acts as a form of RF compression. It operates strictly on the radio frequency signal, distinct from audio frequency (AF) compression which works on the microphone signal before modulation.