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How Slots Work

For most players, playing slots is as complicated as plugging the player’s card into the slot – or depositing it into an online account – and clicking the “Spin”button.

But there’s still a lot going on behind the scenes.

Although the technology has changed over the years, the idea is the same: the reels spin and the mechanism randomly stops the reels in specific positions to form winning (or losing) paylines. Winning combinations are then paid out to players based on the value of the symbols on the payline.

Mechanical machines to the video slot machine revolution

Once, all the slot machines in a casino mechanical. Powered by levers and gears, a braking system stops moving reels, and sensors indicate to the machine which payouts are due depending on the symbols. Especially deep cuts in the discs that controlled the reels would release a shutter inside the machine and pour the jackpot if three or more were to line up in order.

These machines have been almost entirely replaced by Microchip-powered video slots, but the main one remains the same.

The advent of video slots means that mechanical cams, gears and kickers are replaced by microchips that control the entire process from the machine’s motherboard.

After pressing the “Spin” button (or pulling the lever on older and retro video slots models), the computer inside the slot machine selects numbers via the RNG (random number generator).

These numbers are then fed to the computer which correspond to the symbols on the video slot reels. The slot – or computer-then spins the reels to the corresponding symbol and a winning combination or payline is formed. The ‘Step motors’ inside the machine are used to physically stop the game at predetermined, random symbols.

Testing Labs and Audits

Testing laboratories work closely with software suppliers and manufacturers and regulators to ensure that slots are regularly maintained and standards are met.

For a land-based slot, this means compliance testing on hardware and software, jackpot controllers and quality Assurance on electronic gaming devices. The test labs also check the machines as they are under development before they hit the casino floor.

The control of the Odds

One advantage of computer-powered video slots is that payout frequencies can be controlled. Although it is true that slots are random, the way reels and symbols are installed can dramatically change when a jackpot is going to be paid.

Some slot machines can carry a lot of substitute Wilds, for example, while other games can have a small number of bonus icons. The odds, therefore, of triggering a bonus feature or jackpot, can vary dramatically from one machine to another.

But the RNG is also programmed differently for how many times these specific symbols are hit.

Let’s say you play a 5-reel slot that has 20 symbols on each reel. However, the computer program is set so that each of these symbols will be hit with a rating of 1 out of 32.

You can see the number of ‘virtual stops’ is greater than the number of actual symbols, so the more virtual stops, the more chance you have of hitting a certain winning symbol. Of course, with more chances to hit, you also have a great chance to hit a losing symbol too.

For a 5-reel slot, then, your chance to hit this jackpot symbol one on each reel is 1 in 32x32x32x32x32x32 (32 at the power of five) = 1 in 33,554,432. Slots with larger jackpots will have more ‘virtual stops’ and thus the odds increase.

Understand RTP (return to player percentages)

Slots with lots of virtual slots give players the feeling that they can hit the big jackpots, but they also offer more ways to lose too much. This means that big jackpot slots are called ‘high variance’ as they attract with lots of close wins, but in the end will tooth your bankroll over the long run until you hit this big jackpot.

Most slots, however, will have the RTP displayed in their paytables. These ‘return to player percentages’ are notional long-term payments to players by a slot machine.

A slot can carry an RTP of 96% (common in online slots) which means that in the long run, for every $96/100 the machine pays, $4 is deducted.

Laws govern the RTP of slot machines, but land-based machines will generally sit around 85-90%. Online, however, payments are increasing – to about 95% on average.

Of course, just because a slot has a high RTP doesn’t mean you’re a winner right now. You can hit a big winner on a low-RTP game if you’re lucky just like you can A on a high-RTP machine; the question is when do you take the money and run?