A popular
gambling device used in most
casinos. It uses three (or more) independently-spinning reels with a variety of
symbols on them to determine winners. The reels' spinning is activated by pulling a long handle mounted on the side of the machine. Winning involves lining up matching symbols on the "pay line." Common symbols include cherries, bars, bells, and sevens. When they were first introduced, slot machines were purely
mechanical devices, functioning in a similar fashion to tumbler-style
locks. These machines proved to be easy to
cheat, so they rapidly became much more complex. Modern slot machines use computers to guide the reels instead of mechanical methods, and the most
cutting-edge machines are entirely electronic, with
virtual reels instead of physical ones. Some have special play modes or
bonus rounds that have little or no connection to the reels.
Slot machines are extremely popular with the House, because they take up little relative room (Each, anyway), require little maintenance, and can be set to obscenely low payback rates. They also have a very high plays-per-minute ratio compared to table games like Blackjack and Craps. The house edge on slot machines can be changed without any perceptible change in the appearance of the machine. This is part of the reason why slot machines are sometimes called one-armed bandits.
Slot machines have comprised a gradually increasing percentage of casino profits nearly every year for the past 40 years, and are now the greatest individual revenue source. There are several casinos in Las Vegas that have nothing but slot machines. Stay away from those casinos if you value your bankroll...