Components of the Slot Machine

videoslots-logoTypically the devise itself consists of several important parts that could be found on every slot machine worldwide. Such elements are the reels, the payline and the payout display among others. We shall discuss each of those elements and review the basics and some specific features. However, it is important to remember that although the majority of the slot machines are standardized, there are those which are complex and would require additional observation, in order to fully comprehend how the machine works.

The Reels are an essential part of the slot machine, as they are the mechanism that makes the symbols spin and the player’s heart race. Technically known as stepper reels, a slot machine has at least three of them with the potential to add more. The most popular slot machines are those with three or five reels, but there are some machines equipped with as much as ten reels, which are often referred to as Big Berthas, just like the World War I super-heavy mortar.

Each reel has a number of steps or stops, which mark the place where the wheel could stop when it is spun. These steps have a symbol on them, like a card, a fruit, a diamond, basically anything. They could even be blank.

During the genesis of the slot industry reels had only ten symbols on them, but with the development of technology the number has increased drastically. Manufacturers wanted to have more symbols, in order to have more possible combinations, which in turn allowed them to offer bigger winnings and, thus, to attract more players.

Let us look at an example. Let us calculate how many possible combinations a three-reel slot machine with 10 symbols on each wheel has.

Combinations = 10 x 10 x 10 = 1 000

This means the chance of hitting the rarest combination is still 0.1%, which translates into lower maximum winnings for the player, because the machines are designed to be profitable for the company that operates them.

Later the typical slot machine consisted of three reels with 20 symbols on each of them, which translates into 8 000 combinations. An improvement, but it still restricted slot machine operators from giving out major jackpots.

However, with the electronic age and the implementation of microprocessors the possible combinations have grown substantially. For example, a digital reel may have 256 symbols on it or over 16 million possible combinations.

Those calculations only apply for three-wheel slot machines, but as we mentioned before, the one-armed bandits could have up to ten reels, bringing to total count of combinations to 1,20892582×10²⁴!

It is important to note that the number of combinations do not reflect the player’s chances of wining, but the ability to have more combinations. This provides additional flexibility for manufacturers.

The chance of a payout is determined by the frequency of hitting winning combinations. If a winning combination has a relatively high chance of being displayed, the payout amount would be relatively small and vice versa. Having more combinations allows players to win millions with a one-dollar bet.

The hit frequency and the payouts are set by the manufacturers in line with the casino operator’s specifications. Additionally, those metrics can be readjusted anytime by simply changing the chip.

Screenshot of slot machine in casino

The Payline

The horizontal line, which is located onto the glass window in front of the slot machine is called the payline. In order for a spin to win, the winning symbols must align directly behind the line.

While slot machines were new to the world, they had only one payline, right in the middle. Eventually, the number increased to three, five and so on. Some five-reel machines have twenty five paylines. However, to activate more paylines the player must place additional bets. In the common case it is one credit per active line.

The Payout Display

This is where all the wining combinations are displayed and how much they pay according to the placed bet. Special combinations are also listed here.
The display will, in addition, indicate whether or not the machine is progressive and if it is, it will show the total winnable jackpot.

If you are not familiar with “progressive” slot machines, you will find them covered in another article. For the time being, let us just say that progressive machines are linked together and pay a joint jackpot.

The Coin Tray

This must be the favorite part of the slot machine for every gambler, as it is the part where the coins come out. The coin tray is located on the bottom of the machine facing the player and its starts pouring winnings once the “Cash out” button is pressed.

Screenshot of a single payline slot game

The Slots Handle

This is the lever, which makes the reels spin. It is located on the left side of every slot machine and in modern times it is there for more authenticity rather than necessity. While it is true that before the handle was mechanically setting the reels in motion, all it does now is trigger the software and enable the reels to spin.

The Play Buttons

Now, let us go over the buttons that are most commonly found on slot machines. Note that exact names may vary for different models and different manufacturers, but in general, the functions remain the same.

Spin Reels

This is the button that starts the action. Once pressed, it sets the reels in motion.

Play Max Credits/Bet Max Coins

Regardless of its specific name, this button will bet the maximum amount of credits allowed on the particular machine. For example, if the slot machine accepts a maximum bet of five coins and a player presses the button, the machine will deduct five coins from a player’s credits and automatically spin the reels.

Note that this button is only active, if a player has credits in the machine. If it is not the case, more coins need to be inserted before the button becomes active.

Play Two Credits, Play Three Credits

These buttons will usually indicate that the specific slot machine accepts only two or three credits as a maximum bet. If a player presses that button, the result will be the same, as if he has pushed the play max credits/bet max coins.

Play One Credit

This button enables players to bet only one credit per spin. The button is generally found on every slot machine ensuring that everyone has a spot in the casino. It is important to note that unlike the Bet Max Credits button, this one would not set the reel in motion and nothing will happen until the player pulls the lever or presses the Spin Reels button.

Additionally, if a player presses the button twice, the machine will add an extra credit to the next spin and so on.

The Cash Out Button

Basically this button signals the machine that the player is done playing and he wants to either move to another slot machine or stop betting altogether. On older machines when this button was pressed, the one-armed bandit would start paying out the remaining credits in the form of coins. However, the newer machines will simply issue a ticket that the player can later redeem at the cashier’ cage.

The Change Button

This button is located on the far left of the button display and is used to power up the red light on the top of the machine, which in turn signals all casino employees that the player needs service.

Screenshot of slot machine buttons

The Displays

Every machine has several displays located on the front and while different manufacturers may choose different locations, the important thing is that the basic information will always be clearly visible to the player.

Credits Played or Coins Played

When attending a slot machine, a player should always pay attention to the exact number of credits he/she is betting on each spin. For example, if the display shows the number 3, this means three credits are bet on the spin.


This display shows how many remaining credits a player has. When the indicator shows a zero, this means the player must deposit additional coins in order to continue playing. The credit count may be lifted higher either through wining spins, or by inserting extra money into the machine. Each credit will reflect the denomination played. For example, if a player sits on a 25-cent machine and he deposits a $10 bill, the credit display will show that 40 credits have been loaded. Additionally, if a player places three credits on his/her next spin, the display will read 37, while if he/she wins ten credits, the display will show 47.

As we pointed out, the display does not show the money a player has deposited, but rather the amount of credits he bought. If that $10 bill was inserted in a $1 slot machine, the display would read 10, while if it was deposited in a 5-cent machine, the display would show 200.

Pressing the Play One Credit button will automatically deduct one credit from a player’s remaining credits, while the Play Max Credits button deducts the maximum amount of credits that are allowed on one spin on the particular machine.

A player can use his credits only in two ways, by playing and losing them all or by pressing the Cash Out button, which will force the machine to issue a ticket. The ticket represents the actual amount of money a player could redeem at a cashier’s cage.

Winner Paid

This display shows the amount of credits won on the current spin, or the amount of credits that would be added to the player’s credit display.

Insert Coin

This display indicates that the machine is not currently in play and that anyone could start a game by inserting coins or bills into the machine.

Error Code

This message will only be displayed if the machine has malfunctioned and needs the attention of a technician. The display will read a series of numbers or a code that will suggest the nature of the problem, so that the staff member in charge of fixing the machine could repair the device as quickly as possible.

Screenshot a single playline classic slot machine

The Symbols

Although technology has changed the better half of the slot machines, some iconic symbols have persisted through time and could be seen on machines today. For example, the liberty bell symbol, which was on the first slot machine built in 1899, is often used on popular slot machines. Other symbols, which have beaten time, are the cherries, lemons and sevens.

The bar symbol has also survived and nowadays is often modified to double bars, triple bars and similar.

Despite the preservation of many old symbols, a lot more have been born in the imagination of designers, ranging from fruits, numbers, cars, logos, letters, animals and so forth. The number of currently existing symbols is basically endless.

Wild Symbols

Those kind of symbols have become very popular in modern designs and can be used to substitute any other symbol in order to create a wining combination. For example, if a player hits two identical symbols, say cherries, and a “Wild” symbol, the slot will credit the player’s balance with the payable amount for three cherries.
Additionally, some machines use the “Wild” symbols as a multiplier. For example, if a player gets two cherries and a “Wild” symbol, the machine will pay out the amount payable for just three cherries. If a player hits two “Wild” symbols and a cherry, the amount credited will be quadruple.

Any Bar

Another popular symbol is the “Any Bar” symbol. These particular kind of symbols can be used in combination with any of the other bars in order to form a winning combination.


Often slot machines will show “Blank” symbols, which have no winning potential whatsoever.

Screenshot 5 scatters on a slot machine display

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