How Casino Slot Machines Work
Though today's casino slot machines were developed from Charles Fey's Liberty Bell, they function using a totally different system.
Old slot machines work through an elaborate configuration of gears and levers. The central element is a metal shaft, which supports the reels. This shaft is connected to a handle mechanism that gets things moving. A braking system brings the spinning reels to a stop, and sensors communicate the position of the reels to the payout system. A coin detector initially registers that a coin has been inserted and unlocks a brake so the handle can move.
Nowadays, the resulting symbol combinations are dictated by a Random Number Generator (RNG) inside the slot itself, rather than by the activity of the spinning reels.
The RNG is constantly generating random numbers, at a rate of hundreds or maybe thousands per second. As soon as the lever is pulled or the "Play" button is pressed, the most recent random number is used to determine the result. This means that the result varies depending on exactly when the game is played. A fraction of a second earlier or later, and the result would be different.
Considering that the reel display of today's slot machines is controlled by computer software, it is possible to make the slot machine frequently display combinations that are close to winning combinations.
For instance, if the jackpot combination is "7-7-7", a slot machine could be programmed to frequently display "7-7-(non-7)". This can fool the player into thinking they "almost won", teasing them into playing more often.
This practice of showing combinations similar to winning combinations more frequently than would occur randomly is called "near-miss" programming. It has been ruled illegal in Nevada and New Jersey, in the US. The Nevada Gaming Commission did review some machines with this type of programming and refused to authorize them.
Near-miss programming, where a near miss is inaccurately displayed (i.e. the player is shown something that is not an accurate representation of the reel strips) is not allowed in Australia either.
