I see some Berninas that have oscillating hooks, and some that say O/CB, and some that say CB/O and others. What is the difference? I have the 830 Record Electronic and the 1130 (which I gave to my dd), but I don't know what these terms mean. I know the 830 Record is mechanical and the 1130 is computerized, but I don't know what the difference is operation by hooks means.