Classic slot machines are mechanical devices that include three or more reels with different symbols printed around them. The reels are rotated by an impulse of a lever, and if after they stop, a certain pattern of symbols appears in the visible area, the machine pays off a certain amount of money. Slot machines
are operated by coins and contain a currency detector that validates the value of the bet.
The first slot machine was invented in 1895 by Charles Fey from San Francisco. The machine was called Liberty Bell. Its three mechanical reels had pictures of hearts, diamonds, spades, and cracked Liberty Bells. Three bells in a row produced the largest payoff of ten nickels. Liberty Bell was a huge success and gave birth to a prospering industry of mechanical gaming devices. Another early slot machine gave out chewing gums instead of coins. The symbols on the reels were the pictures of fruits that defined the flavor of the chewing gums one could win. Melon and cherry symbols used in modern slot machines derive from this chewing gum machine. The BAR symbol is an early logo of the Bell-Fruit Gum Company. In 1964, the first fully electromechanical slot machine called Money Honey was developed.
Modern computer technologies have allowed building completely different slot machines that simulate the mechanical process displaying it on a video screen and have various extra features. Modern slot machines can accept credit and debit cards and bar-coded paper tickets. The game is no longer activated by the lever. The machines either have a Play button or a touch-screen interface. Some slot machines have become really complicated and may involve skills from the part of the player, but normally the game itself remains a game of chance and only creates the illusion of being dependent on the players decisions.
Each type of slot machine has its proper set of winning combinations and prize values. This set is called pay table and is usually printed on the front of the machine, or in video slots is displayed on the screen, when Pay Table button is pressed.