The Basics
A vending machine uses digital and mechanical energy to release food and other goods to a customer who has paid a specified amount of money for them. Vending machines can essentially "read" dollar bills and coins, which enables them to deposit the money and release the desired item in a process lasting as few as 10 seconds. Many machines can even scan credit and debit cards, as well as return money to the customer when there is a machine malfunction.
Recognizing Money
During a vending transaction, a person first views the items on display and chooses the item he wants. He puts in the money listed for that item, such as $1, and slides the dollar bill into a slot that uses "feeddogs" to accept it. After taking the dollar, the machine uses a laser to scan the dollar. It sends the information to a central computer inside the machine, which reads the dollar as the correct value for the item. The computer confirms it is the correct value (and also that the money is genuine) because it has been programmed to search for certain marks on dollar bills. Moreover, the computer can also distinguish between various coins by an electromagnetic field in the coin slot that reads the metal elements from the coins, which all differ by thickness. These differences prompt the computer to distinguish one coin from another.
Delivering Items
Once the machine accepts the customer's money as valid, it deposits the money into a cash box. It lists the total amount in a digital readout at the front of the machine. The customer selects the item he wants by pushing a button corresponding to that item. Once he does this, the button prompts the computer to retract the metal spirals that hold back the item. The spiral retracts, and the item drops down into the holding box at the bottom of the machine, whereby the customer retrieves it. On the way down, the item passes through a laser beam that notifies the central computer that the customer has his item and the transaction is over.
