Are you asking me? The ALC is a control signal in your radio that reduces the gain in your TX chain and forms part of a negative feedback loop to prevent your transmitter from bring overdriven. You want to keep an eye on it when using SSB, because if the audio drive becomes too high, it can cause excessive ALC action that can result in splatter. For digital modes like PSK where linearity is very important, you don't want any ALC action at all, because it varies the gain in your TX chain which introduces non-linearity.
