Thus the odds of losing symbols appearing on the payline became disproportionate to their actual frequency on the physical reel. These enabled the player to stop each reel, allowing a degree of "skill" so as to satisfy the New Jersey gaming laws of the day which required that players were able to control the game in some way. The electromechanical approach of the s allowed Money Honey to be the first slot machine with a bottomless hopper and automatic payout of up to coins without the help of an attendant. Archived from the original on This new law also banned machines which would automatically play with the button held. Native American casinos located in reservations are not permitted to have slot machines unless the tribe first reaches a pact with the state in which it is located per Indian Gaming Regulatory Act.
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The payment of food prizes was a commonly used technique to avoid laws against gambling 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 "ignorance of the law is no excuse".
Despite the fact that the result of the next use would be displayed on the machine, the courts ruled that "[t]he machine appealed to the player's propensity to gamble, and that is [a] vice.
In , Bally developed the first fully electromechanical slot machine, called Money Honey although earlier machines such as the High Hand draw poker machine by Bally had exhibited the basics of electromechanical construction as early as The electromechanical approach of the s allowed Money Honey to be the first slot machine with a bottomless hopper and automatic payout of up to coins without the help of an attendant.
The prototype was mounted in a full size show-ready slot machine cabinet. The first production units went on trial in the Las Vegas Hilton Hotel. After some "cheat-proofing" modifications, the video slot machine was approved by the Nevada State Gaming Commission and eventually found popularity in the Las Vegas Strip and downtown casinos.
A person playing a slot machine can insert cash, or in ticket-in, ticket-out machines, a paper ticket with a barcode , 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 slot 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 credits the player cash or some other sort of value, such as free spins or extra games.
Free spins are a common feature in modern slot games allowing the user to spin the machine's reels without charge. Many online casinos advertise their free spin rewards and emphasize this feature.
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, , or more hands at one time. Another popular type of machine internationally are video bingo machines, where a player can play Latin style bingo or American style bingo.
Depending on the machine players can play one bingo card or more at a time. Multi-line slot machines have become more popular since the s. These machines have more than one payline, meaning that visible symbols that are not aligned on the main horizontal may be considered for winning combinations. Traditional 3 reel slot machines commonly have three or five paylines, while video slot machines may have 9, 15, 25, or as many as different paylines. Most video slot machines have a themed game, 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.
Most accept variable numbers of credits to play, with 1 to 15 credits per line being typical. The higher the amount bet, the higher the payout will be if the player wins. There are also standard 3 to 5 reel electromechanical machines, of various types. These are the typical "one-armed bandits".
Since about there have been hybrid machines introduced, which combine elements of both video machines and traditional electromechanical machines. One of the main differences between video slot machines and reel machines is in the way payouts are calculated. With reel machines, 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 machines, the fixed payout values are multiplied by the number of coins per line that is being bet. As an example, on the Wheel of Fortune reel machine based on the popular Wheel of Fortune TV game show created by Merv Griffin , 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 machine, 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.
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 attendants to cater to the needs of those who play there. 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 number of available credits to the player.
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. 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.
Some machines feature two or more of these bonus styles as part of the same game. 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. It can be lit by the player by pressing the "service" or "help" button.
Coin hopper is a container where the coins that are immediately available for payouts are held. When a certain preset coin capacity is reached, a coin diverter automatically redirects, or "drops," excess coins into a "drop bucket" or "drop box.
Credit meter is a visual LED display of the amount of money or number of 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. Free Spin is a term used in slot games and online slot games to specify that the spin will be completed without a charge or on the same wager.
Free spins can get triggered by a number of things, each game uses a different method. Usually, landing a number of special symbols on reels is required to activate the free spins bonus round. Mostly scatter symbols are preferred for this activation, although wild symbols or a completely different symbol dedicated for this feature can be used too. In most slot games, landing at least three special symbols on reels is mandatory to trigger the feature.
Once triggered, free spins bonus round award a number of spins free of charge to the player. The number of free spins differ from game to game. If there is the ability to re-trigger free spins during the free spin bonus there is no theoretical limit to the number of free spins obtainable. The spins are automatically used by the game and the player keeps any profit after the spins are complete.
A single free spin is sometimes called a respin. Hand pay refers to a payout made by an attendant or at an exchange point "cage" , rather than by the slot machine itself. 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 replenishment 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 M achine e ntry a uthorization l og is a log of the employee's entries into the machine. Low Level or Slant Top slot machines include a stool so the player has sitdown access. 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 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. Paylines could be of various shapes horizontal, vertical, oblique, triangular, zigzag, etc. 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 refill the machine. Scatter Symbol It is required to place at least two of the same symbols on a pay line to get paid in slot games. However, scatter symbols work differently and award a prize whether they are placed on a pay line or not.
But the player still needs to get at least two of them in modern slot games. The more, the better. Scatter symbols are usually used to award a number of free spins. The number of free spins differs from game to game; i. They can also award coin prizes, based on their number. The prizes are usually small, but they are paid in addition to other winnings.
The scatter symbol is usually a special symbol, which means the wild symbol cannot replace it, although in some games the wild symbol also substitutes for scatters.
Slot variance is a measure of risk associated with playing a slot machine. A low variance slot machine has regular but smaller wins and a high variance slot machine has fewer but bigger wins. 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 a bet over the course of several pulls.
Tilt Electromechanical slot machines usually include an electromechanical " tilt switch ", which makes or breaks a circuit if the machine is tilted or otherwise tampered with, and so triggers an alarm. While modern machines no longer have tilt switches, any kind of technical fault door switch in the wrong state, reel motor failure, out of paper, etc. Theoretical Hold Worksheet A document provided by the manufacturer for all slot machines, which indicates the theoretical percentage that the slot machine should hold based on the amount paid 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.
Wild Symbol Wild symbols act like joker cards in a slot game. Basically, they substitute for all other symbols in the game, usually except for other special symbols, such as scatter and jackpot. They can appear on any of the reels. However, this is not mandatory and can be changed from game to game. In some games, wild symbols can appear only on certain reels. Or, they can appear only during the bonus rounds. The player must refer to the rules and paytable of the game to learn about the landing rules.
Mobile is when the slot machine is hosted for online gambling and it is usually available for use on a phone, tablet, or other portable device. These are often standalone mobile casino applications but are also found as part of the online casino site.
By , HTML5 technology and the advancement of mobile browsers had negated the need for standalone mobile apps. New slots are, by majority, playable on both mobile and desktop devices. 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 can represent many, or all, of the other symbols to complete a winning 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. Historically, all slot machines used revolving mechanical reels to display and determine results.
Although the original slot machine used five reels, simpler, and therefore more reliable, three reel machines quickly became the standard. This limited the manufacturer's ability to offer large jackpots since even the rarest event had a likelihood of 0. Although the number of symbols eventually increased to about 22, allowing 10, combinations,  this still limited jackpot sizes as well as the number of possible outcomes.
In the s, however, slot machine manufacturers incorporated electronics into their products and programmed them to weight particular symbols. Thus the odds of losing symbols appearing on the payline became disproportionate to their actual frequency on the physical reel. A symbol would only appear once on the reel displayed to the player, but could, in fact, occupy several stops on the multiple reel. With microprocessors now ubiquitous, the computers inside modern slot machines allow manufacturers to assign a different probability to every symbol on every reel.
To the player it might appear that a winning symbol was 'so close', whereas in fact the probability is much lower. In the s in the UK machines embodying microprocessors became common. These used a number of features to ensure the payout was controlled within the limits of the gambling legislation. As the coin was inserted into the machine it could go one of two routes, either direct into the cashbox for the benefit of the owner, or alternatively it would go into a channel that formed the payout reservoir, the microprocessor monitoring the number of coins in this channel.
The drums themselves were driven by stepper motors, controlled by the processor and with proximity sensors monitoring the position of the drums. A "look up table" within the software allows the processor to know what symbols were being displayed on the drums to the gambler.
This allowed the system to control the level of payout by stopping the drums at positions it had determined. If the payout channel had filled up, the payout became more generous, if nearly empty, less so thus giving good control of the odds. The video slot machine is a more recent innovation, with no moving parts at all — instead a graphical representation of one appears on screen. In addition, because there are no mechanical constraints on the design of video slot machines, most display five reels rather than three.
This greatly expands the number of possibilities: As there are so many combinations given by five reels, the manufacturers do not need to weight the payout symbols although some may still do so.
Instead, higher paying symbols will typically appear only once or twice on each reel, while more common symbols, earning a more frequent payout, will appear many times.
Video slot machines typically encourage the player to play multiple "lines", so rather than simply taking the middle of the three symbols displayed on each reel, a line could go from top left to bottom right, or any of the other patterns specified by the manufacturer. As each symbol is equally likely, there is no difficulty for the manufacturer in allowing the player to take any or all of the possible lines on offer — the long-term return to player will be the same. The difference for the player is that the more lines he plays the more likely he is to get paid on a given spin — though of course he is betting more in the first place.
To avoid the feeling that the player's money is simply ebbing away whereas a payout of credits on a single line machine would be bets, and the player would feel they had made a substantial win, on a 20 line machine, it would only be 5 bets and would not seem significant , manufacturers commonly offer bonus games, which can return many times their bet.
The player is encouraged to keep playing to reach the bonus: All modern machines are designed using pseudo random number generators "PRNGs" , which are constantly generating a sequence of simulated 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. It is important that the machine contains a high-quality RNG implementation, because all PRNGs must eventually repeat their number sequence,  and if the period is short, or the PRNG is otherwise flawed, an advanced player may be able to 'predict' the next result.
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. Most machines are designed to defeat this by generating numbers even when the machine is not being played, so the player cannot tell where in the sequence they are, even if they know how the machine was programmed.
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. The winning patterns on slot machines — the amounts they pay and the frequencies of those payouts — 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. Within some EGM development organizations this concept is referred to simply as "par.
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. Other jurisdictions, including Nevada, randomly audit slot machines to ensure that they contain only approved software. Historically, many casinos, both online and offline, have been unwilling to publish individual game RTP figures, making it impossible for the player to know whether they are playing a "loose" or a "tight" game.
Since the turn of the century some information regarding these figures has started to come into the public domain either through various casinos releasing them—primarily this applies to online casinos—or through studies by independent gambling authorities.
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. 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 guarded secrets, it is possible that the advertised machines with high return to player simply increase the probabilities of these jackpots.
The added advantage is that these large jackpots increase the excitement of the other players. This game, in its 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: Most players assume the likelihood increases proportionate to the payout. The one midsize payout that is designed to give the player a thrill is the It is programmed to occur an average of once every plays. In contrast the The highest payout of 2, The player who continues to feed the machine is likely to have several midsize payouts, but unlikely to have a large payout.
He quits after he is bored or has exhausted his bankroll. Despite the fact that they are confidential, occasionally a PAR sheet is posted on a website. They have limited value to the player, because usually a machine will have 8 to 12 different possible programs with varying payouts. In addition, slight variations of each machine e.
The casino operator can choose which EPROM chip to install in any particular machine to select the payout desired. The result is that there is not really such a thing as a high payback type of machine, since every machine potentially has multiple settings.
Without revealing the proprietary information, he developed a program that would allow him to determine with usually less than a dozen plays on each machine which EPROM chip was installed. Then he did a survey of over machines in 70 different casinos in Las Vegas.
He averaged the data, and assigned an average payback percentage to the machines in each casino. The resultant list was widely publicized for marketing purposes especially by the Palms casino which had the top ranking. 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. 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 , the Nevada Gaming Commission began working with Las Vegas casinos on technology that would allow the casino's management 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.
Often machines are linked together in a way that allows a group of machines to offer a particularly large prize, or "jackpot". Each slot machine in the group contributes a small amount to this progressive jackpot , awarded to a player who gets, for example, a royal flush on a video poker machine or a specific combination of symbols on a regular or nine-line slot machine.
The amount paid for the progressive jackpot is usually far higher than any single slot machine could pay on its own. In some cases multiple machines are linked across multiple casinos. In these cases, the machines may be owned by the manufacturer, who is responsible for paying the jackpot. The casinos lease the machines rather than owning them outright.
Casinos in New Jersey, Nevada, and South Dakota now offer multi-state progressive jackpots, which now offer bigger jackpot pools.
Mechanical slot machines and their coin acceptors were sometimes susceptible to cheating devices and other scams.