From this answer I understand that the reflex mirror of a DSLR is actually not reflecting all the light, but it passes a certain amount on to the AF sensor. So if the reflex mirror can pass light, ...
As I understand every DSLR has a separate, smaller sensor that handles phase detection focusing. Where is it located? If this location is different for every DSLR, and therefore this broad question ...
Do all autofocus cameras need motors to drive the lens? I would have thought today's modern electronics rendered motors obsolete.