Ask the Slot Expert: Four ways to determine the result of a spin on a slot machine

This week let's take a look at four ways the results of a spin on a slot machine can be determined.

The first and oldest (and probably most prevalent) method is the Random Number Generator (RNG), the digital implementation of the method used in the mechanical and electro-mechanical slots that ruled the slot floor until the computer-controlled slots took over. The old machines contained a mechanism that attempted to stop the reels at a random place on each spin. The machines also had mechanisms to read where each reel stopped and then pay out anything won.

Computer control of the slot machine came in the 1980s. These machines got rid of the "random stop" mechanism and replaced it with the RNG. The machines used a number generated by the RNG to determine where to stop a reel. The machines still have a mechanism to read where the reels have stopped, but now it's not used to determine the result of the spin. The computer already knows where the reels were supposed to stop. It's used to ensure that the reels stopped where the computer told them to stop and, if not, the machine will raise a Reel Tilt error.

The RNG is so simple. But it's also considered to be gambling in some places. So when these places wanted to have gambling without having gambling, they had to look for another way to determine where to stop the reels on a slot machine.

If a state allowed charitable bingo games, then Native American tribes could run bingo games too. Many opened bingo halls. The real money is in spinning reels, though, so they looked for a way to turn a bingo drawing into a slot machine.

Enter the Class II slot machines. The Indian Gaming Regulatory Act defined three classes of gaming. Class I is social gaming for minimal prizes. Class II is bingo and pull tabs. Class III is gambling -- table games and RNG-based slot machines and pretty much anything else that doesn't fit in Class I or Class II.

To find the results of a spin, a Class II slot machine joins a bingo drawing that is conducted on a central server. The central server draws the bingo numbers and sends them down to all of the machines participating in the drawing. A machine determines its results by the pattern filled on its electronic bingo card. These patterns aren't necessarily the fun ones, like the Champagne Glass and the Dollar Sign, just a pattern on the card.

The central server won't conduct a drawing until a minimum number of players have joined it. Players who like to play in the wee hours have told me that they sometimes have to wait to see the results of a spin until enough players have joined a drawing. By contrast, the RNG is not only always ready to supply a result, it's constantly generating new results even when its machine is not being played.

Now let's say you're a state that wants slot machines but not gambling. Your lottery sells scratch-off tickets. Is there any way to turn a scratcher into a slot machine?

This method is known as Finite Outcome. A central server maintains a pool of possible outcomes, like the boxes of scratch-off tickets the lottery commission prints for a particular scratch-off game. When a player hits the Spin button on a machine, the machine requests an outcome from the central server. The central server chooses an outcome from the pool appropriate for the game on that machine. The machine then spins the reels and stops them on the outcome received from the central server.

What happens when a pool is used up on the central server? No problem. Just like Lay's potato chips, it will make more. When a pool is depleted, the central server just creates a new pool.

I thought I had seen it all in how jurisdictions allow slot machines without allowing gambling, but I learned of a new one last week. Say you're in a state that allows betting on horse races. Is there any way to turn the results of horse races into results on a slot machine?

I wrote about this method, Historical Horse Racing, last week. Let's take a more detailed look this week. This description is based on the method described in the patent cited below.

To determine the results of a spin, the method uses three races with 10 horses each. Each finishing place in each race is assigned to a bit in a binary number. For example, Race 1 Place 1 may be assigned to bit 1 and Race 2 Place 5 may be assigned to bit 20. The alignment is arbitrary.

For each race, there is a predicted order in which the horses will finish. And, of course, there is the actual order in which the horses finished.

The method checks to see which predictions are correct. If the prediction for Race 1 Place 1 was horse 6 and horse 6 did finish first in Race 1, the method assigns a 1 to bit 1. If the prediction for Race 2 Place 5 was horse 3 and horse 9 actually came in fifth, the method assigns a 0 to bit 20.

To recap, there are 3 races with 10 horses each, so there are a total of 30 predictions. Each prediction corresponds to a bit in a binary number, so the binary number has 30 bits. When a prediction is correct, its corresponding bit is set to 1. Otherwise the bit is 0.

After all of the predictions have been evaluated, we have a 30-bit binary number. (A sample 30-bit binary number is 100010000000100010101111000000.) There is a table of results that tells us the result assigned to each number. The method looks up the result that corresponds to the number calculated from evaluating the predictions.

There is another step that complicates the process. Can you imagine players entering in 30 predictions for each spin? Most people just want to hit the Spin button. The system will calculate the initial predictions for each race. The patent allows for the player to alter the predictions, but I can't imagine any player doing that.

I'm still shaking my head over this method.

Source: Patent: System and Method of Wagering on a Plurality of Events

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