You've never been to an Automat? Well, this is how these things work...(scroll on).
Photo from Bernice Abbott, Automat, 1936, Collection of Martin Z. Margulies
 

You deposit coins in a slot and take your food selection out of the adjacent compartment. It's really pretty simple and the food is usually tasty.
Graphic from Lumitone Photography, New York, New York

We recommend the Salisbury Steak...and mac and cheese.