This is all roughly right except that when you say "incredibly quickly on the time scale of milliseconds" it's often actually microseconds. This sort of work i

This is all roughly right except that when you say "incredibly quickly on the time scale of milliseconds" it's often actually microseconds. This sort of work is done either in custom hardware or FPGAs - that's the only way you can precisely control the phase offset of signals (and measure it). They can respond very quickly.