Slots Guide

A slot machine (American), fruit machine (British), or poker machine (Australian) is a casino gambling machine with three or more reels which spin when a button is pushed.

Slots are also known as one-armed bandits because slot machines were originally operated by a lever on the side of the machine (the one arm) instead of a button on the front panel, and because of their ability to leave the gamer penniless. Many modern machines still have a legacy lever in addition to the button.
Slot machines include a currency detector that validates the coin or money inserted to play. The machine pays off based on patterns of symbols visible on the front of the machine when it stops. Modern computer technology has resulted in many variations on the slot machine concept.

Slot machines are the most popular gambling method in casinos and constitute about 70 percent of the average casino’s income. It is estimated that thirty percent or more of the profits from gambling machines come from problem gamblers.

Slot History

Sittman and Pitt of Brooklyn, New York, U.S. developed a gambling machine which was a precursor to the modern slot machine. It contained five drums holding a total of 50 card faces and was based on poker.

This machine proved extremely popular and soon many bars in the city had one or more of the machines bar-side. Players would insert a nickel and pull a lever, which would spin the drums and the cards they held, the player hoping for a good poker hand.

There was no direct payout mechanism, so a pair of kings might get the player a free beer, whereas a royal flush could pay out cigars or drinks, the prizes wholly dependent on what was on offer at the local establishment.

To make the odds better for the house, two cards were typically removed from the deck: the ten of spades and the jack of hearts, which cut the odds of winning a royal flush by half. The drums could also be re-arranged to further reduce a player’s chance of winning.

The first one-armed bandit was invented in 1887 by Charles Fey of San Francisco, California, U.S., who devised a much simpler automatic mechanism. Due to the vast number of possible wins with the original poker card based game, it proved practically impossible to come up with a way to make a machine capable of making an automatic pay-out for all possible winning combinations.

Charles Fey devised a machine with three spinning reels containing a total of five symbols – horseshoes, diamonds, spades, hearts and a Liberty Bell, which also gave the machine its name. By replacing ten cards with five symbols and using three reels instead of five drums, the complexity of reading a win was considerably reduced, allowing Fey to devise an effective automatic payout mechanism.

Three bells in a row produced the biggest payoff, ten nickels. Liberty Bell was a huge success and spawned a thriving mechanical gaming device industry. Even when the use of these gambling devices was banned in his home state after a few years, Fey still couldn’t keep up with demand for the game elsewhere.
Another early machine gave out winnings in the form of fruit flavoured chewing gums with pictures of the flavours as symbols on the reels. The popular cherry and melon symbols derive from this machine. The BAR symbol now common in slot machines was derived from an early logo of the Bell-Fruit Gum Company.

The payment of food prizes was a commonly used technique to avoid anti-gambling laws in a number of states, and for this reason a number of gumball and other vending machines were regarded with mistrust by the courts.
The two Iowa cases of State v. Ellis and State v. Striggles are both used in classes on criminal law to illustrate the concept of reliance upon authority as it relates to the axiomatic ignorantia juris non excusat. In these cases, a mint vending machine was declared to be a gambling device due to the fact that by (internally manufactured) chance the machine would occasionally give the next user a number of tokens exchangeable for more candy.

Despite the fact that the result of the next use would be displayed on the machine, both courts ruled that “The inducement for each play was the chance that by that play the machine would be set to indicate that it would pay checks on the following play.

The thing that attracted the player was the chance that ultimately he would receive something for nothing. The machine appealed to the player’s propensity to gamble, and that is [a] vice.”
In 1964, Bally developed the first fully electromechanical slot machine called Money Honey. The new electromechanical approach allowed Money Honey to be the first slot machine with a bottomless hopper and automatic payout, of up to 500 coins, without the help of an attendant.

The popularity of this machine led to the increasing predominance of electronic games, and the side lever soon became vestigial.

The first video slot machine to offer a second-screen bonus round was Reel ‘Em In developed by WMS Industries Inc. in 1996.

A person playing a slot machine purchases the right to play by inserting coins, cash, or in newer Ticket-In, Ticket-Out machines, a bar-coded paper ticket, into a designated slot on the machine. The machine is then activated by means of a lever or button, or on newer machines, by pressing a touchscreen on its face.

The game itself may or may not involve skill on the player’s part — or it may create the illusion of involving skill while only being a game of chance.

The object of the game is to win money from the machine. The game usually involves matching symbols, either on mechanical reels that spin and stop to reveal one or several symbols, or on simulated reels shown on a video screen.

The symbols are usually brightly colored and easily recognizable, such as images of fruits, numerals or letters, and simple shapes such as bells, diamonds, or hearts; newer video-based machines use animated cartoon characters and images of popular actors or singers (in the case of themed slot machines, as described below).

Most games have a variety of winning combination of symbols, often posted on the face of the machine (or available on a different screen, accessible by touching a button on the main touchscreen, on video slot machines). If a player matches a combination according to the rules of the game, the slot machine pays the player cash or some other sort of value, such as extra games.

There are many different kinds of gambling slot machines in places such as Las Vegas (as well as casinos modeled after those in Las Vegas, including those operated on Native American reservations).

Some of the most popular are the video poker machines, in which players hope to obtain a set of symbols corresponding to a winning poker hand. Depending on the machine, players can play one, 100, or more hands at one time.

Becoming more popular since the 1990′s are the multi-line slots. These slots have more than one payline. Reel slots commonly have three or five paylines, while video slots have 9, 15, 25, or as many as 100 different paylines.

Most video slots are themed slots, some of which feature graphics and music based on popular entertainers, motion pictures or TV programs (The Addams Family, I Dream of Jeannie, Happy Days, etc.) with a bonus round. Most accept variable amounts of credit to play with 1 to 15 credits per line being typical. The higher the amount bet, the higher the payout will be.

There are also standard 3 – 5 reel electromechanical slot machines, of various types. These are the typical “one-armed bandits”. Since about 2005 there have been hybrid machines introduced, which combine elements of both video slots and traditional electromechanical slots.

One of the main differences between video slots and reel slots is in the way payouts are calculated. With reel slots, the only way to win the maximum jackpot is to play the maximum number of coins (usually 3, sometimes 4, or even 5 coins per spin). With video slots, the fixed payout values are multiplied by the number of coins per line that is being bet.
In other words: on a reel slot, it is to the player’s advantage to play with the maximum number of coins available. On video slots, it is recommended to play as many individual lines as possible, but there is no benefit to the player in betting more than one credit per line with regards to calculating the payout amounts.

There are some isolated cases where a video slot machine requires the maximum number of credits per spin to be inserted to win the largest payout, but those are the exception.
As an example, on the “Wheel of Fortune” reel slot, the player must play 3 coins per spin to be eligible to trigger the bonus round and possibly win the jackpot. On the Wheel of Fortune video slot, the chances of triggering the bonus round or winning the maximum jackpot are exactly the same regardless of the number of coins bet on each line.
Larger casinos offer slot machines with denominations from $.01 (penny slots) all the way up to $100.00 or more per credit. Large denomination slot machines are usually cordoned off from the rest of the casino into a “High Limit” area, often with a separate team of hosts to cater to the needs of the high-rollers who play there.
Slot machines common in casinos at this time are more complicated. Most allow players to accept their winnings as credits, which may be “spent” on additional spins.
In the last few years, new multi-denomination slot machines have been introduced. With these slot machines, the player can choose the value of each credit wagered (the stake) from a list of options.

Based upon the player’s selection, the slot machine automatically calculates the number of credits the player receives in exchange for the cash inserted and displays the amount of available credits to the player. For example, a player could choose to wager one dollar per game on a nickel slot machine.
This eliminates the need for a player to find a specific denomination of a particular slot machine; they can concentrate on simply finding the machine and setting the denomination once they decide to play.
Recently, some casinos have chosen to take advantage of a concept commonly known as “tokenization,” where one token buys more than one credit. A casino can configure slot machines of numerous different denominations to accept the same type of token. For example, all penny, nickel, quarter, and dollar slot machines could be configured to accept dollar tokens. This significantly reduces a casino’s inventory costs and coin handling costs.
A tokenized slot machine automatically calculates the number of credits the player receives in exchange for the token inserted and displays the amount of available credits to the player. When a player chooses to collect his credits (by pressing a “Cash Out” button), the slot machine will automatically divide the number of credits on the credit meter by the value of one token and return the result to the patron. Any remainder is known as “residual credits” and cannot be collected. Residual credits must be either played or abandoned.

Bonus is a special feature of the particular game theme, which is activated when certain symbols appear in a winning combination. Bonuses vary depending upon the game. Some bonus rounds are a special session of free spins (the number of which is often based on the winning combination that triggers the bonus), often with a different or modified set of winning combinations as the main game, and often with winning credit values increased by a specific multiplier, which is prominently displayed as part of the bonus graphics and/or animation.
In other bonus rounds, the player is presented with several items on a screen from which to choose. As the player chooses items, a number of credits is revealed and awarded. Some bonuses use a mechanical device, such as a spinning wheel, that works in conjunction with the bonus to display the amount won.
Candle is a light on top of the slot machine. It flashes to alert the operator that change is needed, hand pay is requested or a potential problem with the machine. Carousel refers to a grouping of slot machines, usually in a circle or oval formation.
Coin hopper is a container where the coins that are immediately available for payouts are held. The hopper is a mechanical device that rotates coins into the coin tray when a player collects credits/coins (by pressing a “Cash Out” button). When a certain preset coin capacity is reached, a coin diverter automatically redirects, or “drops”, excess coin into a “drop bucket” or “drop box”. (Non-functional coin hoppers can still be found even on games that exclusively employ Ticket-In Ticket-Out technology, as a legacy vestige.)
Credit meter is a visual LED display of the amount of money or credits on the machine. On video reel machines this is either a simulated LED display, or represented in a different font altogether, based on the design of the game graphics.

Drop bucket or drop box is a container located in a slot machine’s base where excess coins are diverted from the hopper.

Typically, a drop bucket is used for low denomination slot machines and a drop box is used for high denomination slot machines. A drop box contains a hinged lid with one or more locks whereas a drop bucket does not contain a lid. The contents of drop buckets and drop boxes are collected and counted by the casino on a scheduled basis.

EGM is used as a short-hand for “Electronic Gaming Machine”.
Hand pay refers to a payout made by a slot attendant or cage, rather than the slot machine. A hand pay occurs when the amount of the payout exceeds the maximum amount that was preset by the slot machine’s operator. Usually, the maximum amount is set at the level where the operator must begin to deduct taxes. A hand pay could also be necessary as a result of a short pay.
Hopper fill slip is a document used to record the replenishments of the coin in the coin hopper after it becomes depleted as a result of making payouts to players. The slip indicates the amount of coin placed into the hoppers, as well as the signatures of the employees involved in the transaction, the slot machine number and the location and the date.
MEAL book (machine entry authorization log) is a log of the employee’s entries into the machine
Low Level or Slant Top slot machines include a stool so you can sit and play. Stand Up or Upright slot machines are played while standing.
Optimal play is a payback percentage based on a gambler using the optimal strategy in a skill-based slot machine game.
Payline is a straight or zig-zagged line that crosses through one symbol on each reel, along which a winning combination is evaluated. Classic spinning reel machines usually have up to nine paylines, while video slot machines may have as many as one hundred.
Rollup is the process of dramatizing a win by playing sounds while the meters count up to the amount that has been won.
Short pay refers to a partial payout made by a slot machine, which is less than the amount due to the player. This occurs if the coin hopper has been depleted as a result of making earlier payouts to players. The remaining amount due to the player is either paid as a hand pay or an attendant will come and re-fill the machine.
Taste is a reference to the small amount often paid out to keep a player seated and continuously betting. Only rarely will machines fail to pay out even the minimum placed bet over the course of several pulls.
Tilt In the old mechanical days, slot machines had tilt switches. While modern machines no longer have tilt switches, any kind of mechanical failure (door switch in the wrong state, reel motor failure, etc) is still called a “tilt”.
Theoretical Hold Worksheet is a document provided by the manufacturer for all slot machines, which indicates the theoretical percentage that the slot machine should hold based on adequate levels of coin-in. The worksheet also indicates the reel strip settings, number of coins that may be played, the payout schedule, the number of reels and other information descriptive of the particular type of slot machine.
Weight count is an American term, referring to the dollar amount of coins or tokens removed from a slot machine’s drop bucket or drop box and counted by the casino’s hard count team through the use of a weigh scale.

Each machine has a table that lists the number of credits the player will receive if the symbols listed on the pay table line up on the pay line of the machine. Some symbols are wild and will pay if they are visible in any position, even if they are not on the pay line.

Especially on older machines, the pay table is listed on the face of the machine, usually above and below the area containing the wheels. Most video machines display the pay table when the player presses a “pay table” button or touches “pay table” on the screen; some have the pay table listed on the cabinet as well.

Random Number Generator

It is a common belief that the odds on a machine have something to do with the number of each kind of symbol on each reel, but in modern slot machines this is no longer the case.

Modern slot machines are computerized, so that the odds are whatever they are programmed to be. In modern slot machines, the reels and lever are present for historical and entertainment reasons only.

The positions the reels will come to rest on are chosen by a Random Number Generator (RNG) contained in the machine’s software.
The RNG is constantly generating random numbers, at a rate of hundreds or perhaps thousands per second. As soon as 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.
Some professional gamblers observe that the RNG actually produces quite predictable sequences of “random” numbers.

This behavior is due to poor algorithm design. All RNGs (so-called pseudorandom number generators or PRNGs) must in theory eventually repeat their number sequence (see Art of Computer Programming Vol 2 Chap 3), but it is relatively easy to build PRNGs with periods (that is, the length of a sequence before it repeats) that are so long that no computer, however fast, could complete a single period before the end of the universe.
Having access to the PRNG code and seed values Ronald Dale Harris, a former slot machine programmer, discovered equations for specific gambling games like Keno that allowed him to predict what the next set of selected numbers would be based on the previous games played. However, this is impossible for most machines, because the RNG picks numbers even when the machine is not being played, so the player cannot tell where in the sequence they are.
Virtual Reels
Old mechanical slot machines had a set number of reels containing a set number of symbols, each equally likely to appear on the payline after each spin. In the 1980s, however, slots makers incorporated electronics into their products and programmed them to weigh particular symbols. Thus the odds of losing symbols appearing on the payline became disproportionate to their actual frequency on the physical reel.
In 1984 Inge Telnaes received a patent for a device titled, “Electronic Gaming Device Utilizing a Random Number Generator for Selecting the Reel Stop Positions.” International Gaming Technology IGT bought the Telnaes patent and now all slot manufacturers using what has come to be known as Talneas mapping or reel mapping must license the patent from IGT.

The 1984 patent granted on this technology (United States Patent No. 4 448 419) states: “It is important to make a machine that is perceived to present greater chances of payoff than it actually has within the legal limitations that games of chance must operate.”
The other advantage of a virtual reel has to do with the number of stops. The original slot machine had three physical reels with 10 symbols on each reel. Although the number of stops was increased over the years to about 22, the mechanical device still limited the number of possible outcomes.

A virtual reel can have up to 256 virtual stops per reel. The physical reel has only 103=1,000 possible combinations. The manufacturer is limited to the maximum payout that he can offer since it could happen every 1,000 plays.

If the jackpot paid 100:1 then the machine will have already used 10% of the outcome space on this one win. The original machine kept 25% as the house edge. The virtual reel with 256 virtual stops has 3256 = 16,777,216 final positions. The manufacturer could choose to offer a million to one payout confident that it will only happen every 16.7 million plays.

Payout percentage

Slot machines are typically programmed to pay out as winnings 82–98% of the money that is wagered by players. This is known as the “theoretical payout percentage” or RTP, “Return To Player”. The minimum theoretical payout percentage varies among jurisdictions and is typically established by law or regulation.

For example, the minimum payout in Nevada is 75%, and in New Jersey, 78%. The winning patterns on slot machines—the amounts they pay and the frequencies of those pay-outs—are carefully selected to yield a certain fraction of the money played to the “house” (the operator of the slot machine), while returning the rest to the players during play. Suppose that a certain slot machine costs $1 per spin.
It can be calculated that over a sufficiently long period, such as 1,000,000 spins, that the machine will return an average of $950,000 to its players, who have inserted $1,000,000 during that time. In this (simplified) example, the slot machine is said to pay out 95%.

The operator keeps the remaining $50,000. Within some EGM-development organizations this concept is referred to simply as “par”. “Par” also manifests itself to gamblers as promotional techniques: “Our ‘Loose Slots’ have a 93% pay-back! Play now!” It is worth noting that the “Loose Slots” actually may describe a very few anonymous machines in a particular bank of EGMS.

A slot machine’s theoretical payout percentage is set at the factory when the software is written.
Changing the payout percentage after a slot machine has been placed on the gaming floor requires a physical swap of the software or firmware, which is usually stored on an EPROM but may be loaded onto non-volatile random access memory (NVRAM) or even stored on CD-ROM or DVD, depending on the capabilities of the machine and the applicable regulations.

Based on current technology, this is a time-consuming process and as such is done infrequently. In certain jurisdictions, such as New Jersey, the EPROM has a tamper-evident seal and can only be changed in the presence of Gaming Control Board officials. Other jurisdictions, including Nevada, randomly audit slot machines to ensure that they contain only approved software.
The return to player is not the only statistic that is of interest. The probabilities of every payout on the pay table is also critical. For example, consider a hypothetical slot machine with a dozen different values on the pay table. However, the probabilities of getting all the payouts are zero except the largest one.

If the payout is 4,000 times the input amount, and it happens every 4,000 times on average, the return to player is exactly 100%, but the game would be relatively dull to play. Also, most people would not win anything, and having entries on the paytable that have a return of zero would be deceptive.
As these individual probabilities are closely gaurded secrets, it is possible that the advertised machines with high return to player simply increase the probabilities of these jackpots. The casino could legally place machines of a similar style payout and advertise that some machines have 100% return to player. The added advantage is that these large jackpots increase the excitement of the other players.
The table of probabilities for a specific machine are called the Paytable and Real Strips sheet, or PARS. The Wizard of Odds revealed the PARS for one commercial slot machine, an original International Gaming Technology Red White and Blue machine.

This game, in it’s original form, is obsolete, so these specific probabilities do not apply. He only published the odds after a fan of his sent him some information provided on a slot machine that was posted on a machine in the Netherlands. The psychology of the machine design is quickly revealed.
There are 13 possible payouts ranging from 1:1 to 2,400:1. The 1:1 payout comes every 8 plays. The 5:1 payout comes every 33 plays, whereas the 2:1 payout comes every 600 plays. Most players assume the likelihood increases proportionate to the payout. The one mid-size payout that is designed to give the player a thrill is the 80:1 payout. It is programmed to occur an average of once every 219 plays.
The 80:1 payout is high enough to create excitement, but not high enough that it makes it likely that the player will take his winnings and abandon the game. More than likely the player began the game with at least 80 times his bet (for instance there are 80 quarters in $20).

In contrast the 150:1 payout occurs only on average of once every 6,241 plays. The highest payout of 2,400:1 occurs only on average of once every 643=262,144 plays since the machine has 64 virtual stops. The player who continues to feed the machine is likely to have several mid-size payouts, but unlikely to have a large payout. He quits after he is bored or has exhausted his bankroll.
One reason that the slot machine is so profitable to a casino is that the player must play the high house edge and high payout wagers along with the low house edge and low payout wagers. In a more traditional wagering game like craps, the player knows that certain wagers have almost a 50/50 chances of winning or losing, but they only pay a limited multiple of the original bet (usually no higher than three times). Other bets have a higher house edge, but the player is rewarded with a bigger win (up to thirty times in craps).

The player can choose what kind of wager he wants to make. A slot machine does not afford such an opportunity.
Theoretically, the operator could make these probabilities available, or allow the player to choose which one so that the player is free to make a choice. However, no operator has ever enacted this strategy. Different machines have different maximum payouts, but without knowing the odds of getting the jackpot, there is no rational way to differentiate.
In many markets where central monitoring and control systems are used to link machines for auditing and security purposes, usually in wide area networks of multiple venues and thousands of machines, player return must usually be changed from a central computer rather than at each machine. A range of percentages is set in the game software and selected remotely.
In 2006, the Nevada Gaming Commission began working with Las Vegas casinos on technology that would allow the casino’s slot manager to change the game, the odds, and the payouts remotely. The change cannot be done instantaneously, but only after the selected machine has been idle for at least four minutes. After the change is made, the machine must be locked to new players for four minutes and display an on-screen message informing potential players that a change is being made.

Slots Rules

Slots is the easiest casino game to learn and play. It’s also one of the online casinos’ most popular game today.
First you place your bet. Typically you can bet one, two or more coins (up to five or ten on some slot machines). Depending on the machine, the coins may be $.05, $0.5, $5 or other values. So if you bet five coins on a $1 machine, your bet is five dollars.
Next you click a button to spin the wheels. This is the same as pulling the arm on a real slot machine. Now all you do is wait and see if you win!
Where the wheels stop determines if you win and how much. The goal is to get the symbols (cherries, numbers and so on) to line up on the payline in one of the winning combinations listed on the pay table. Each game will have its own pay table. For example, three bars in a row may pay 20 to 1.

Three cherries in a row may pay 3 to 1. Some machines have three or five paylines, or pay on the diagonal. Check the casino rules for details. To get this information, you usually just click a help button or visit preview games page.
Some online casinos offer so-called progressive jackpots. That means that a jackpot builds as more and more players play the casino’s progressive machines. The first person to hit the winning combination (e.g. 777 or others) wins the total jackpot. To be eligible for the jackpot you usually have to play the maximum number of coins. Then the jackpot resets to a lower value and starts to increase again as more people play.
The result of each spin of the wheels is determined by a computer program that generates random results. This is true for both online slots games and slot machines found in terrestrial casinos. The machines can easily be set by the casino to generate whatever payout they choose. For example, they may set it to 96%. That means for every 100 dollars bet, the machine will, on average, pay out 96 dollars. The other four dollars goes to the casino and that’s how they make their profit. Of course, that’s just on average. It’s possible, if Lady Luck is on your side, to make hundreds or even thousands of dollars with just one spin. On some large progressive jackpots you can win even millions, as Anthony P who won $1,594,649.21 at Captain Cooks Casino on May 30, 2002.

Slots Strategies

It’s a common myth that slot machines are the worst gamble in a casino. The truth is that making bad bets at the craps table or blackjack table can give far worse odds than any slot machine. The odds you get when playing slots are similar to those for roulette.
Another commonly held belief is that a slot machine that just gave a big payout won’t pay out again for a while. Actually, statistically speaking, the odds are the same for every spin and every spin is completely random and independent of all past spins. So there’s no way to predict the next spin and a jackpot is just as likely to be hit right after the last one was hit as it is after a thousand dry spins.
Strategies
Most slot machines reward you for playing the maximum number of coins. For example the jackpot may pay 2000 coins with 2 coins played, but 4000 coins when 3 coins are played. If you don’t feel comfortable playing the maximum coins you might consider moving down to a machine that accepts lower-value coins so you can play the maximum.

For example instead of playing one coin at a dollar machine, play the maximum number of coins at a quarter machine. Some online casinos let you play for nickels (All Slots Casino has some of the lowest betting limits starting from 1¢).
Play at casinos that advertise the best payout percentages. These casinos are eager for your business are willing to reward you with better payouts. The build-in payouts for slots games are different in each casino for each slot game. Some of the casinos pays out well over 99% for some slots (e.g. Zodiac Casino) while others rip up to 10% on each spin! Check out our payouts page to find casinos with the highest payout percentages for Slots.
If you’re playing a progressive machine, remember that you’ll probably have to bet the maximum number of coins to be eligible to win the big jackpot. You may find the largest currently available jackpot at our Jackpots page.