Have you been thinking how it works. Here is some picture about it. It is not really complex. The component is about sweeping (remove fallen pins), table, table shield, pit, pit elevator, pin storage and ball returns. Thanks to Gottfried Schmidt that first introduced the automatic pinsetter. So, people don’t need to do it physically like in picture below. It is a hard job to focus to control the pins stability.
Image source and more complete informations: howstuffworks