How Do Modern Slot Machines Work

  1. Slot Machines How They Work
  2. How Do Modern Slot Machines Work
  3. How Do Modern Slot Machines Work In
  4. How Do Modern Slot Machines Work Kids
  1. To learn how to beat slot machines, you need to first know how they work. Slots are amongst the most popular casino games throughout the world, both in land-based and online casinos.
  2. Most reel spinners take up to two or three coins at a time while video slots can take 45, 90, and even 500 credits at a time. Nearly all slot machines are fitted with currency acceptors - slide a bill into the slot, and the equivalent amount of credits is displayed on a meter.

All about Slot Machines. How they work, Common myths, and Strategies. Last update: October 2018. In the 1980's slot machines surpassed table games like craps and blackjack as the most popular game in the casino. Modern graphics and mobile-compatibility. Modern slot machines use a computer to generate random numbers, and these determine the outcomes of the game. The important thing to remember is that the results are truly random. The game doesn’t work on any kind of cyclical basis, and slot machine jackpots don’t become due. Slots don’t get hot or cold, either.

Introduction to How Slot Machines Work

In these series of posts, I continue to answer the most common questions about slot machines asked via Google searches. This post explains the simple question of how slot machines work.

In this post, I will discuss the operational components of a slot machine from the point-of-view of a slots player. Meaning, the various interface areas on the front of a slot machine. These player interface areas include:

  • Service Light
  • Bonus Display (Optional)
  • Pay Table
  • Players Club
  • Results
  • Play Console
  • Ticket In, Ticket Out (TITO)

Additional relatively minor interface areas are not listed or shown below. These areas are the locations audio speakers, audio volume control (optional), display lights, lever arm, and a hearing aid jack to accommodate those with a hearing disability.

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Service Light

A slot machine’s service light is generally located at the very top of a slot machine to be easily visible to casino employees. Because of this uppermost location, it’s also known as the candle within slots terminology.

Slots players can switch on the service light by activating the service button on the player console. Or, it will enable by itself if the player wins a hand pay jackpot or the slot machine develops a service fault. Faults might include lack of paper, a full cash-in condition, mechanical or electronic tampering, or an internal electronic failure such as CPU overheating, etc.

Modern casinos have a slot attendant call/dispatcher communication system using a headset and microphone. This setup is helpful for spotting problems on the casino floor. An activated service light automatically notifies the casino operating system. The casino dispatcher then informs the slot attendant responsible for that section of the casino.

Once the notification is sent out, a lit candle is of little practical use. At best, it guides the responding slot attendant the last few feet to the customer needing attention and, also, provides some reassurance to the waiting customer.

Slots players may activate the candle for a multitude of reasons. In general, they do so to deliberately call a slot attendant to their location, for any of a host of reasons only limited by imagination.

Pro-Tip #1: Service Light

Sometimes slots players need to leave a slot machine briefly but don’t want to give it up to someone else. If this break is relatively brief, say 10-15 minutes, use the service button to call over a slot attendant. The slot attendant can temporarily lock up the slot machine at the request of the player.

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The slot machine can be unlocked later by the player via insertion of only their service card … or after 10-15 minutes when the temporary lockout automatically expires. For the specific length of lockout times, ask any slot attendant at your casino.

Bonus Display Area

If a specific slot machine has a bonus round available, then it will often have a second display area. Video slots may use the same primary display screen but abruptly display the bonus round game theme instead. However, video slots most often have a secondary display screen available for bonus rounds.

The Bonus Display area is optional and dependent upon the specific slot machine model. The location of this bonus display varies. More often than not, it is high up on the slot machine to be viewable by other players from a distance.

Casinos offset their losses by offering slot machines with bonus round display visible from a distance. Frankly, wins on these highly visible and usually loud bonus displays are seen by many. This obvious win encourages other casino patrons to play slot machines.

Pro-Tip #2: Bonus Round

Bonus rounds generally cannot be activated unless that slot machine’s maximum credits are bet. By not betting maximum credits, the player automatically lowers their odds of winning.

If betting maximum credits on a specific denomination slot machine is not affordable, pick another affordable slot machine. I discuss this approach in detail at Choosing Slot Machines.

Pay Table Area

The Pay Table area lists information on the jackpot amounts for specific reel combinations. It can also display some or all of the game theme rules. This area may be permanently displayed on the slot machine, or possibly only available through an interactive series of images available by touchscreen.

In either case, all possible wins may or may not be displayed. Sometimes the list is highly abbreviated, and displays only the highest jackpots, due to space limitations. Other times, mainly with touchscreen displays, a series of images can be switched between to view every possible winning combination.

However, pay tables typically provide the highest value jackpot. Slot machine game themes with multipliers or “wild” reel symbols have their most top value jackpots being the result of these reel symbols. Alternatively, it may not show all multipliers or “wild” symbols in the tabulated list of win-reel combinations. Instead, they may be in writing along the edge of the paytable interface area.

But, with large touchscreens has come the capability to provide full paytable information along with game theme rules. Some slot machines now have this feature and, perhaps, more will have it in the future.

Many paytables show the number of credits that would be won for a specific combination of reel symbols. Or, they may show a monetary amount. In either case, these tables have separate columns for winning combinations dependent upon how many credits are bet. The farright column typically shows the winning jackpots available when betting maximum credits.

Some examples of credit and denomination combinations are:

  • 1-credit slot machines having a $100 denomination
  • 3-credit slot machines having a $5 denomination
  • 5-credit “quarter slots” having a $0.25 denomination
  • 300-credit “penny slots” have a $0.01 denomination

Pro-Tip #3: Pay Tables

Slot Machines How They Work

Frankly, learning the paytable of any slot machines played is a relatively easy way to improve the odds of winning at slots. Many typical slots players believe there is no skill involved in winning at slot machines. Casinos gently foster this misunderstanding, as it is to their benefit. Don’t fall for it.

Traditionally, slots players find it acceptable to play slot machines with visual succinct paytables. Frankly, casinos would instead have their customers spend their time playing a game they don’t understand.

The casino isn’t making money if a player spends time studying or reading until they do understand rather than playing the machine.

One easy-to-learn skill to improve the odds of winning at slots is choosing which slots to play based on their paytables. I discuss this in detail at Choosing Slot Machines.

Players Club Area

The Players Club area contains a card reader, numbered keypad, and a small display. A security feature of players club cards is for players to choose a PIN to enter when they wish to access their player account.

Newer-style slot machines have a touchscreen display, which removes the need for a physical keypad. Meaning, it’s part of the touchscreen display.

Bets can be made on a slot machine without a players’ club card. At most casinos, it typically is not required. Neither is the PIN needed to play the device or view basic information. For example, a running total of reward points earned during the current play session is generally on display.

The PIN is required, however, to:

  • access certain portions of player’s casino account
  • transfer banked funds
  • activate “free play” provided by the casino as a complimentary gift

Results Area

The Results interface area is where the reel combinations are seen after making a bet. Whether a video slot machine or a slot machine with physical reel, this is where the results of a bet are provided.

Interpreting whether a reel combination is a winner requires an understanding of the paytable. This result is fundamental to how slot machines work.

Of course, the slot machine will immediately display the results. A small display beneath the reels shows:

  • the total amount of money or credits available in the machine
  • how many credits most recently bet
  • the jackpot amount won if any

Jackpots are usually in credits, where each credit equals the denomination of the machine rather than the amount bet, as well as a monetary amount.

Player Console

The Play Console typically has physical buttons, a cash/ticket reader, and a ticket printer. The buttons include:

  • Cash Out for requesting the removal of any player funds in the machine
  • Service to request a casino attendant
  • A Series of Buttons for selecting the number of credits to bet, or placing the maximum possible bet
  • Cash Out for removing any remaining bankroll
  • Repeat to making another bet for the same credit(s)
  • Denomination to select a specific bet denomination (optional)

The player console may have several possible button configurations, dependent upon the model of the slot machine. Given how often game themes are switched to maintain the interest of players over time, it is common for player consoles to be standardized over many machines within a casino.

How Do Modern Slot Machines Work

Also, it is becoming common for consoles to have embedded displays visible through their semi-transparent button covers. This array of small screens are linked together to show visually stunning composite images displayed across the entire array of buttons.

Ticket In, Ticket Out (TITO)

By the beginning of the 21st Century, the use of coins was removed from casinos. This removal was for the sake of convenience of both the casino and customers. Both had issues with handling so many coins. Customers because of the difficulties inherent with carrying so much weight, but also gambling delays due to full (or empty) slot machine coin hoppers.

Casinos had issues with coins as well, including customer complaints due to delays caused by a full (or empty) slot machine coin hopper. This inconvenience was a coin logistics issue, which also included higher costs of maintaining a larger vault space and coin processing equipment and services. As casinos became more popular, coins became more difficult for everyone.

As a result, Ticket-In, Ticket-Out technology was pulled into casinos. They are now integral to how slot machines work. This automation is the same technology that was beginning to be seen in Automated Teller Machines (ATMs). Once proven out, this slot machine technology was here to stay like so many others.

Summary of How Slot Machines Work

I’ve discussed the operational components of a slot machine from the point-of-view of a slots player. This explanation of how slot machines work included the various player interface areas on the front of a typical slot machine.

There are additional relatively minor interface areas. These areas include audio speakers, audio volume control (optional), display lights, lever arm, and a hearing aid jack to accommodate those with a hearing disability.

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Have fun, be safe, and make good choices!
By Jon H. Friedl, Jr. Ph.D., President
Jon Friedl, LLC

Slot machines are one of the most popular parts of a casino. Whether you’re a professional or a gambling newbie, slots are the perfect opportunity to try your luck, promising fast-paced thrills with no skill involved. But have you ever wondered how these well-loved machines work?

The roaring success of online slots is a testament to how much we enjoy the slot machines in our bars and casinos. The technology may have finally made the shift into the digital world, however, this is simply the latest development in the long history of slot machines.


If you want to find out more, read on. In this article, we’ll be explaining how slot machines actually work – and why these games of chance are even harder than you thought!

How many parts does a slot machine have?

How Do Modern Slot Machines Work In

In general, traditional slot machines are made up of six parts. When you insert your money, these parts work together to activate the mechanism:

  1. The coin slot. Modern slot machines also usually have an in-built card machine.
  2. The lever. On early machines, pulling the lever would physically trigger the reels to spin, but this is now motorized.
  3. The reels. Slot machines contain three reels, each one notched so that it can spin around a metal shaft (and eventually stop at the desired position).
  4. The brakes. The braking mechanism causes the reels to stop one at a time.
  5. Payout trigger. These are a series of metal pins that can ‘read’ the depth of the notches on the reels in order to work out the required payout amount.
  6. Winning line. This is the combination of symbols that you’ll need to get to win the jackpot.

What happens when you pull the lever?

When you insert your money, the lever is unlocked so you can start to play. Once you pull the lever, a motor automatically causes the reels to spin (on some old-fashioned machines, the lever itself spins the reels).

A braking system brings each reel to a stop, one at a time. At this point, the metal payout trigger pins are used to detect the depth of the notches on each reel. This means the machine is able to identify the reels which the player has spun, triggering the correct payout. (The notch that signifies the jackpot is often a lot deeper than the other notches).

What are computerized slot machines?

How Do Modern Slot Machines Work Kids

Today, most new slot machines use a computerized system, rather than the motorized mechanism which drove more traditional machines.

These computerized slots rely on a random number generator, which means that each spin has a truly equal chance of hitting the jackpot. As soon as the machine is switched on, this generator is constantly cycling through a wide range of numbers. When you pull the lever, it stops suddenly and ‘remembers’ the last three numbers it cycled through.

These numbers will determine the position of the reels, with each number divided by a set amount in order to reach a value which corresponds to one of the notches on the reel.

This technology means your chance of hitting the jackpot is staggeringly small – but if games of chance are how you get your thrills, this should only add to the fun!

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