Slot Machine RNG

Understanding the RNG for slots is one of the first steps in becoming an educated gambler.

For the first 80 years or so of their existence, slot machines were mechanical devices. They had spinning reels that stopped at random, and the results were determined by where those reels stopped. In a sense, this machine was a random number generator, or RNG, but we don’t think of simple machines when we think of RNGs. We think of tiny computer that generate thousands of numbers per second as RNGs.

The reality is that any mechanical device that generates random numbers is a “random number generator”. That includes roulette wheels and dice. But in modern slot machine games, random number generators are limited to those tiny computers generating those thousands of numbers per second. When you hit the spin button (or pull the lever) the number that the computer is processing at that second determines the outcome of your spinning reels before they even stop spinning.

In fact, the spinning reels and everything else you see on a slot machine are just there for show. The random number generator determines all of the outcomes.

Casinos love this device, because it increases the flexibility they have with their games. When you’re using huge metal reels inside of a box, you’re limited to the number of symbols you can use just because of size limitations. Computers have no real size limitations, so a modern day slot machine can have five reels with fifty different symbols (or more) on each. They can also feature bonus games and paylines that would be impossible to determine using an old school slot machine game.

Inge Telnaes and the “Electronic Device Utilizing a Random Number Generator for Selecting the Reel Stop Positions”

Inge Telnaes worked for Bally in the 1970s, and his job was to come up with a way to create larger jackpots for slot machines while still making a profit. When you’re dealing with mechanical reels with a limited number of symbols, the amounts of your jackpots are limited by the odds you’re capable of generating, and a machine with reels big enough to hold that many symbols was just too big to be practical.

Telnaus’ solution was to use imaginary reel strips with lots of symbols on them. Each symbol had numbers attached to them. The symbols that needed to come up more often had more numbers attached to them, and vice versa. This enabled a machine to have twenty or thirty different symbols, some of which might come up once in every five spins, and others which might only come up once in every twenty or thirty spins.

Telnaus was clearly better at programming and brainstorming than he was at coming up with catchy names for his inventions. He named this new way of managing slot machine results the “Electronic Device Utilizing a Random Number Generator for Selecting the Reel Stop Positions.”

This invention revolutionized the slot machine industry, and all modern slot machine games use some type of random number generator (RNG) to determine results.

Par Sheets and How They Work

When a modern game designer creates a slots game, they create something called a “par sheet” to set the rules and payouts for that particular game. One might think that “par” is an acronym, but it’s impossible to find an authoritative source that states what this acronym means. Gambling expert (and occasional slot machine designer) Michael Shackleford theorizes that “par” might stand for “pay table and reel strips”, or it might stand for “probability accounting report”, or it might just use the word’s meaning of expected result. (Like “par” in golf, or “par for the course”.)

The par sheet for a slot machine game includes several pieces of information. One of the most important is the amount of money that the machine takes. Some slots are designed to be played for a penny a spin, some for a nickel, some for a quarter, and so on. The payout percentages chance with the denomination size, usually offering a higher payout percentage for larger wagers.

The par sheet also includes the number of symbols on each reel. Some games might have as few as 35 symbols per reel, while others might have as many as 256 symbols per reel.

Of course, the payback percentage is also listed on the par sheet, and it varies from machine to machine. The sheet also includes how often the machine hits a win of some kind. This might vary from 5% to 20% of the time, but it’s not limited to those percentages. This is called “hit frequency”. A game with a high hit frequency has frequent small wins, which keeps players interested.

The par sheet also includes how many plays per jackpot, the jackpot amount, and how many plays per bonus, and the bonus amounts. For example, a game might be set to hit a jackpot once out of every 46,000 spins. On the other hand, it might be set to hit a jackpot once out of every 8,000,000 spins.

The important thing to remember amount these numbers is that they don’t cycle through. In other words, you might think that a game that’s set to hit a jackpot once out of every 46,000 spins would hit a jackpot immediately after the 45,999th spin, but that’s not how it works. Every spin is an independent event with a 1 in 46,000 chance of winning, regardless of what happened on the previous spin.

You’re just as likely (and just as unlikely) to hit a jackpot on the 46,001st spin as you are on the 46,000th. Confusion about the idea of “independent events” has resulted in a lot of bogus winning systems being sold to a lot of suckers. The only people making money from that deal are the systems-sellers.