They are actually just writing data to the concentric tracks, but just timing the steps between the tracks very carefully. When making a copy, you couldn't get

They are actually just writing data to the concentric tracks, but just timing the steps between the tracks very carefully. When making a copy, you couldn't get the steps to sync up and so the timing for the steps would all be broken. High end commercial copiers really didn't come into play until 1984-5.