How does Vending Machines work?

Have you ever wondered how vending machines work? Ever wondered how does the machine recognizes the currency? How does it determine which coin or bill did you insert? Here's a brief explanation:

Bills:

• Bills are printed with magnetic ink, and different denominations generate distinctive magnetic fields.
• Ultraviolet scanning technology can determine the different fluorescent properties of bills.
• Digital cameras can reference the optical patterns in bills with a database of authentic patterns.

Coins:

• The machine checks its diameter
• Weight
• Thickness
• Composition
• Some say it has two magnets to slow down the speed because of its magnetic content. Only Iron is magnetic, I don't think coins are made out of Iron.