How Does Casino Slot Machines Work

• How Does Casino Slot Machines Work At Home
• Casino Slot Machines For Sale

Slot machines are the most common games where you earn progressive jackpot wins. Slots that have the progressive jackpot are the newer videos with many paylines, they also have bonus rounds and other new features. They can be found in reel machines, table games and video poker machines. Most modern slot machines are designed to look and feel like the old mechanical models, but they work on a completely different principle. The outcome of each pull is actually controlled by a central computer inside the machine, not by the motion of the reels. The computer uses step motors to turn each reel and stop it at the predetermined point. So, How Do Casino Slots Actually Work? Well, as you may know, all casino slots have reels that spin during each round unless you play on autospin, which is a topic for another day. Most slots come with three reels although more and more new casinos now come with up to five reels. Slot machines are an extremely popular form of gambling. The premise is simple: you insert a coin, pull a lever, and reap in cash rewards if the symbols on the reels align in a certain way. Slot machines test your luck and intuition, and, despite the simple rules, they are not boring in the slightest.

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.

Keep Reading … or Listen Instead!

Subscribe to my Professor Slots podcast at Apple Podcasts | Google Podcasts | Spotify | Amazon Music | Amazon Audible | Gaana | Stitcher | Pandora | iHeart Radio | Tune-In | SoundCloud | RadioPublic | Deezer | RSS and everywhere else you find your podcasts!

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.

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 far–right 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

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.

How Does Casino Slot Machines Work At Home

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.

Casino Slot Machines For Sale

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.

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.

Slot machines are the most common games where you earn progressive jackpot wins. Slots that have the progressive jackpot are the newer videos with many paylines, they also have bonus rounds and other new features. They can be found in reel machines, table games and video poker machines. Most modern slot machines are designed to look and feel like the old mechanical models, but they work on a completely different principle. The outcome of each pull is actually controlled by a central computer inside the machine, not by the motion of the reels. The computer uses step motors to turn each reel and stop it at the predetermined point. So, How Do Casino Slots Actually Work? Well, as you may know, all casino slots have reels that spin during each round unless you play on autospin, which is a topic for another day. Most slots come with three reels although more and more new casinos now come with up to five reels. Slot machines are an extremely popular form of gambling. The premise is simple: you insert a coin, pull a lever, and reap in cash rewards if the symbols on the reels align in a certain way. Slot machines test your luck and intuition, and, despite the simple rules, they are not boring in the slightest.

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.

Keep Reading … or Listen Instead!

Subscribe to my Professor Slots podcast at Apple Podcasts | Google Podcasts | Spotify | Amazon Music | Amazon Audible | Gaana | Stitcher | Pandora | iHeart Radio | Tune-In | SoundCloud | RadioPublic | Deezer | RSS and everywhere else you find your podcasts!

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.

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 far–right 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

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.

How Does Casino Slot Machines Work At Home

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.

Casino Slot Machines For Sale

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.

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.

Related Articles from Professor Slots

Other Articles from Professor Slots

• Previous: Where Were Slot Machines Invented Historically?
• Next: Why Do Slot Machines Say Bar on Their Reels?

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