Phase-locked loop

A phase-locked loop is like a fancy machine that makes sure two different signals stay in sync. It does this by constantly adjusting one of the signals to match the other. For example, if you have a clock that is ticking away, it produces a signal. If you also have a fan motor somewhere else in your house that is going round and round, it also produces a signal. The machine will make sure both signals are in the same rhythm, so that the fan is always spinning in time with the clock.